Vladimir Kostsov | St.Petersburg state University (Russian Federation) (original) (raw)

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Papers by Vladimir Kostsov

Research paper thumbnail of Reply on RC2

Research paper thumbnail of Reply on RC1

Research paper thumbnail of Comment on acp-2021-387

A.: Retrieval of the land-sea contrast of cloud liquid water path by applying a physical inversio... more A.: Retrieval of the land-sea contrast of cloud liquid water path by applying a physical inversion algorithm to combined zenith and off-zenith ground-based microwave measurements, Atmos. Meas. Tech. Discuss. [preprint],

Research paper thumbnail of The reply to the anonymous referee #2 (RC4)

Research paper thumbnail of The reply to the anonymous referee #3 (RC2)

Research paper thumbnail of Emission Monitoring Mobile Experiment (EMME): an overview and results of the St. Petersburg megacity campaigns of 2019-2020 (Russia)

Research paper thumbnail of The reply to the anonymous referee #1 (RC2)

Research paper thumbnail of The reply to the anonymous referee #3 (RC1)

Research paper thumbnail of Reply on RC1

Liquid water path (LWP) is one of the most important cloud parameters. The knowledge on LWP is cr... more Liquid water path (LWP) is one of the most important cloud parameters. The knowledge on LWP is critical for many studies including global and regional climate modelling, weather forecasting, modelling of hydrological cycle and interactions between different components of the climate system: the atmosphere, the hydrosphere, and the land surface. Satellite observations by the SEVIRI and AVHRR instruments have already provided the evidences of the systematic difference between the LWP values derived over the land surface and over the Baltic Sea and major lakes in Northern Europe during both cold and warm seasons. The goal of the present study is to analyse the phenomenon of the LWP horizontal inhomogeneities in the vicinity of various water bodies in Northern Europe making focus on the temporal and spatial variation of LWP. The objects of investigation are water bodies and water areas located in Northern Europe which are different in size and other characteristics: Gulf of Finland, Gulf of Riga, the Neva River bay, lakes Ladoga, Onega, Peipus, Pihkva, Ilmen, and Saimaa. The input data are the LWP values of pure liquid-phase clouds derived from the space-borne observations by the SEVIRI instrument in 2011-2017 during daytime. The study revealed that in general the mean values of the land-sea LWP gradient are positive during all seasons (larger values over land, smaller values over water surface). However, the negative gradients were also detected over several relatively small water bodies during cold (winter) season. The important finding is the positive trend of the land-sea LWP gradient detected within the time period 2011-2017. The analysis of intra-seasonal features revealed special conditions on the territory of the Gulf of Finland where in June and July large and moderate positive LWP gradients prevail over negative ones while in August positive and negative gradients are much smaller (in terms of absolute values) and occur with equal frequency. This result can lead to the conclusion about possible common physical mechanisms that drive the land-sea LWP difference in the Baltic Sea region at small distances from the coastline. The diurnal cycle of the LWP land-sea gradient has been detected in June and July while there was no evidence for it in August. For several specific cases, atmospheric parameters over the mesoscale domain comprising Gulf of Finland and several lakes have been simulated with the numerical model ICON in limited area and weather prediction mode.

Research paper thumbnail of Retrieval of the land-sea contrast of cloud liquid water path by applying a physical inversion algorithm to combined zenith and off-zenith ground-based microwave measurements

Combined zenith and off-zenith ground-based observations by modern microwave radiometers provide ... more Combined zenith and off-zenith ground-based observations by modern microwave radiometers provide an opportunity to study horizontal inhomogeneities of the humidity field in the troposphere and of the cloud liquid water path (LWP) spatial distribution. However, practical applications are difficult and require thorough analysis of the information content of measurements, assessment of errors of data processing algorithm and the development of the quality control procedures. In this study we analyse the application of our LWP retrieval algorithm based on the inversion of the radiative transfer equation to the problem of detection of the LWP horizontal inhomogeneities by means of ground-based microwave observations in the vicinity of a coastline of a water object of medium size. The study is based on data acquired by the microwave radiometer RPG-HATPRO which is located in the suburbs of St.Petersburg, Russia, at 2.5 km distance from the coastline of the Neva Bay (the Gulf of Finland) and is operating in angular scanning mode in the vertical plane. The retrieval setup is organised in such a way that zenith and off-zenith measurements provide equal sensitivity to atmospheric parameters. The optimal elevation angles for off-zenith observations are selected. The possibility to detect LWP horizontal inhomogeneity, namely the LWP land-sea contrast, for different measurement geometries (elevation angles) and values of cloud base height is analysed. It is shown that ground-based microwave observations in the vicinity of a coastline can be a valuable tool for validation of the space-borne measurements of the LWP land-sea contrast if three principal requirements are met: (a) the multi-parameter physical inversion method is used for retrieving LWP; (b) rigorous bias correction and quality control procedures are applied to the retrieval results; (c) the information on the cloud base height is available. As a result of processing the microwave measurements at the observational site of St.Petersburg State University, the monthlyaveraged values of the LWP land-sea difference have been obtained for summer months within the period 2013-2021. For 24 out of 25 months of high quality observations, the LWP land-sea monthly difference is positive (larger values over land and smaller values over water) and can reach 0.06-0.07 kg m-2. The estimations of the LWP land-sea contrast obtained from the ground-based microwave measurements at the observational site of St.Petersburg University are in very good agreement with the values of the LWP land-sea contrast obtained from the multi-year space-borne measurements by the SEVIRI instrument (Spinning Enhanced Visible and InfraRed Imager) in the region of the Neva Bay (the Gulf of Finland) in June

Research paper thumbnail of Inter-annual, seasonal and diurnal features of the cloud liquid water path over the land surface and various water bodies in Northern Europe as obtained from the satellite observations by the SEVIRI instrument in 2011–2017

. Liquid water path (LWP) is one of the most important cloud parameters. The knowledge on LWP is ... more . Liquid water path (LWP) is one of the most important cloud parameters. The knowledge on LWP is critical for many studies including global and regional climate modelling, weather forecasting, modelling of hydrological cycle and interactions between different components of the climate system: the atmosphere, the hydrosphere, and the land surface. Satellite observations by the SEVIRI and AVHRR instruments have already provided the evidences of the systematic difference between the LWP values derived over the land surface and over the Baltic Sea and major lakes in Northern Europe during both cold and warm seasons. The goal of the present study is to analyse the phenomenon of the LWP horizontal inhomogeneities in the vicinity of various water bodies in Northern Europe making focus on the temporal and spatial variation of LWP. The objects of investigation are water bodies and water areas located in Northern Europe which are different in size and other characteristics: Gulf of Finland, Gulf of Riga, the Neva River bay, lakes Ladoga, Onega, Peipus, Pihkva, Ilmen, and Saimaa. The input data are the LWP values of pure liquid-phase clouds derived from the space-borne observations by the SEVIRI instrument in 2011–2017 during daytime. The study revealed that in general the mean values of the land-sea LWP gradient are positive during all seasons (larger values over land, smaller values over water surface). However, the negative gradients were also detected over several relatively small water bodies during cold (winter) season. The important finding is the positive trend of the land-sea LWP gradient detected within the time period 2011–2017. The analysis of intra-seasonal features revealed special conditions on the territory of the Gulf of Finland where in June and July large and moderate positive LWP gradients prevail over negative ones while in August positive and negative gradients are much smaller (in terms of absolute values) and occur with equal frequency. This result can lead to the conclusion about possible common physical mechanisms that drive the land-sea LWP difference in the Baltic Sea region at small distances from the coastline. The diurnal cycle of the LWP land-sea gradient has been detected in June and July while there was no evidence for it in August. For several specific cases, atmospheric parameters over the mesoscale domain comprising Gulf of Finland and several lakes have been simulated with the numerical model ICON in limited area and weather prediction mode. These simulations have clearly demonstrated the LWP land-sea gradient and have pointed out less stability of the atmosphere over land surfaces.

Research paper thumbnail of Detection of the cloud liquid water path horizontal inhomogeneity in a coastline area by means of ground-based microwave observations: feasibility study

Atmospheric Measurement Techniques

Research paper thumbnail of The reply to the anonymous referee #2 (RC2)

Research paper thumbnail of The reply to the anonymous referee #1 (RC1)

Research paper thumbnail of Emission Monitoring Mobile Experiment (EMME): an overview and first results of the St. Petersburg megacity campaign-2019

results of the EMME observational campaign using the mass balance approach. The CO 2 emission flu... more results of the EMME observational campaign using the mass balance approach. The CO 2 emission flux for St. Petersburg as an area source was estimated to be 89 ± 28 kt km −2 yr −1 , which is 2 times higher than the corresponding value in the EDGAR database. The experiment revealed the CH 4 emission flux of 135 ± 68 t km −2 yr −1 , which is about 1 order of magnitude greater than the value reported by the official inventories of St. Petersburg emissions (∼ 25 t km −2 yr −1 for 2017). At the same time, for the urban territory of St. Petersburg, both the EMME experiment and the official inventories for 2017 give similar results for the CO anthropogenic flux (251 ± 104 t km −2 yr −1 vs. 410 t km −2 yr −1) and for the NO x anthropogenic flux (66 ± 28 t km −2 yr −1 vs. 69 t km −2 yr −1).

Research paper thumbnail of The Use of Linear Regression Relations Derived from Model and Experimental Data for Retrieval of the Water Content of Clouds from Ground-Based Microwave Measurements

Atmospheric and Oceanic Optics

Research paper thumbnail of Cross-comparison of cloud liquid water path derived from observations by two space-borne and one ground-based instrument in Northern Europe

Atmospheric Measurement Techniques Discussions

Cloud liquid water path (LWP) is one of the target atmospheric parameters retrieved remotely from... more Cloud liquid water path (LWP) is one of the target atmospheric parameters retrieved remotely from ground-based and space-borne platforms using different observation methods and processing algorithms. Validation of LWP retrievals is a complicated task since a cloud cover is characterised by strong temporal and spatial variability while remote sensing methods have different temporal and spatial resolution. An attempt has been made to compare and analyse the collocated LWP data delivered by two satellite instruments SEVIRI and AVHRR together with the data derived from microwave observations by the ground-based radiometer RPG-HATPRO. The geographical region of interest is the vicinity of St.Petersburg, Russia, where the RPG-HATPRO radiometer is operating. The study is focused on two problems. The first one is the so-called scale difference problem which originates from dissimilar spatial resolutions of measurements. The second problem refers to the land-sea LWP gradient. The radiometric site is located 2.5 km from the coastline where the effects of the LWP gradient are pronounced. A good agreement of data obtained at the microwave radiometer location by all three instruments (HATPRO, SEVIRI and AVHRR) during warm and cold seasons is demonstrated (the largest correlation coefficient 0.93 was detected for HATPRO and AVHRR data sets). The analysis showed no bias of the SEVIRI results with respect to HATPRO data and a high bias (0.013-0.017 kg m-2) of the AVHRR results for both warm and cold seasons. The analysis of LWP maps plotted on the basis of the SEVIRI and AVHRR measurements over land and water surfaces in the vicinity of St.Petersburg revealed the unexpectedly high LWP values delivered by AVHRR during cold season over the Neva river bay and over the Saimaa Lake and the abnormal land-sea LWP gradient in these areas. For the detailed evaluation of atmospheric state and ice cover in the considered geographical regions during the periods of ground-based and satellite measurements, reanalysis data were used. It is shown that the most probable reason for the observed artifacts in the AVHRR measurements over water/ice surfaces is the coarse resolution of the land-sea and snow/ice masks used by the AVHRR retrieval algorithm. The influence of a cloud field inhomogeneity on the agreement between the satellite and the groundbased data was studied. For this purpose, the simple estimate of the LWP temporal variability was used as a measure of the

Research paper thumbnail of Cloud liquid water path in the sub-Arctic region of Europe as derived from ground-based and space-borne remote observations

Atmospheric Measurement Techniques

Tropospheric clouds are a very important component of the climate system and the hydrological cyc... more Tropospheric clouds are a very important component of the climate system and the hydrological cycle in the Arctic and sub-Arctic. Liquid water path (LWP) is one of the key parameters of clouds urgently needed for a variety of studies, including the snow cover and climate modelling at northern latitudes. A joint analysis was made of the LWP values obtained from observations by the SEVIRI satellite instrument and from ground-based observations by the RPG-HATPRO microwave radiometer near St Petersburg, Russia (60 • N, 30 • E). The time period of selected data sets spans 2 years (December 2012-November 2014) excluding winter months, since the specific requirements for SEVIRI observations restrict measurements at northern latitudes in winter when the solar zenith angle is too large. The radiometer measurement site is located very close to the shore of the Gulf of Finland, and our study has revealed considerable differences between the LWP values obtained by SEVIRI over land and over water areas in the region under investigation. Therefore, special attention was paid to the analysis of the LWP spatial distributions derived from SEVIRI observations at scales from 15 to 150 km in the vicinity of St Petersburg. Good agreement between the daily median LWP values obtained from the SEVIRI and the RPG-HATPRO observations was shown: the rms difference was estimated at 0.016 kg m −2 for a warm season and 0.048 kg m −2 for a cold season. Over 7 months (February-May and August-October), the SEVIRI and the RPG-HATPRO instruments revealed similar diurnal variations in LWP, while considerable discrepancies between the diurnal variations obtained by the two instruments were detected in June and July. On the basis of reanalysis data, it was shown that the LWP diurnal cycles are characterised by considerable interannual variability.

Research paper thumbnail of Cross-validation of two liquid water path retrieval algorithms applied to ground-based microwave radiation measurements by the RPG-HATPRO instrument

International Journal of Remote Sensing

Research paper thumbnail of Quality assessment of integrated water vapour measurements at St. Petersburg site, Russia: FTIR vs. MW and GPS techniques

Atmospheric Measurement Techniques Discussions

The cross-comparison of different techniques for atmospheric integrated water vapour (IWV) measur... more The cross-comparison of different techniques for atmospheric integrated water vapour (IWV) measurements is the essential part of their quality assessment protocol. We inter-compare the synchronised data sets of IWV values measured by Fourier-transform infrared spectrometer Bruker 125 HR (FTIR), microwave radiometer RPG-HATPRO (MW) and global navigation satellite system receiver Novatel ProPak-V3 (GPS) at St. Petersburg site between August 2014 and October 2016. Generally, all three techniques agree well with each other and therefore are suitable for monitoring IWV values at St. Petersburg site. We show that GPS and MW data quality depends on the atmospheric conditions; in dry atmosphere (IWV smaller than 6 mm), these techniques are less reliable at St. Petersburg site than the FTIR method. We evaluate the upper bound of statistical measurement errors for clear-sky conditions as 0.33 ± 0.03 mm (2.0 ± 0.3 %), 0.54 ± 0.03&t...

Research paper thumbnail of Reply on RC2

Research paper thumbnail of Reply on RC1

Research paper thumbnail of Comment on acp-2021-387

A.: Retrieval of the land-sea contrast of cloud liquid water path by applying a physical inversio... more A.: Retrieval of the land-sea contrast of cloud liquid water path by applying a physical inversion algorithm to combined zenith and off-zenith ground-based microwave measurements, Atmos. Meas. Tech. Discuss. [preprint],

Research paper thumbnail of The reply to the anonymous referee #2 (RC4)

Research paper thumbnail of The reply to the anonymous referee #3 (RC2)

Research paper thumbnail of Emission Monitoring Mobile Experiment (EMME): an overview and results of the St. Petersburg megacity campaigns of 2019-2020 (Russia)

Research paper thumbnail of The reply to the anonymous referee #1 (RC2)

Research paper thumbnail of The reply to the anonymous referee #3 (RC1)

Research paper thumbnail of Reply on RC1

Liquid water path (LWP) is one of the most important cloud parameters. The knowledge on LWP is cr... more Liquid water path (LWP) is one of the most important cloud parameters. The knowledge on LWP is critical for many studies including global and regional climate modelling, weather forecasting, modelling of hydrological cycle and interactions between different components of the climate system: the atmosphere, the hydrosphere, and the land surface. Satellite observations by the SEVIRI and AVHRR instruments have already provided the evidences of the systematic difference between the LWP values derived over the land surface and over the Baltic Sea and major lakes in Northern Europe during both cold and warm seasons. The goal of the present study is to analyse the phenomenon of the LWP horizontal inhomogeneities in the vicinity of various water bodies in Northern Europe making focus on the temporal and spatial variation of LWP. The objects of investigation are water bodies and water areas located in Northern Europe which are different in size and other characteristics: Gulf of Finland, Gulf of Riga, the Neva River bay, lakes Ladoga, Onega, Peipus, Pihkva, Ilmen, and Saimaa. The input data are the LWP values of pure liquid-phase clouds derived from the space-borne observations by the SEVIRI instrument in 2011-2017 during daytime. The study revealed that in general the mean values of the land-sea LWP gradient are positive during all seasons (larger values over land, smaller values over water surface). However, the negative gradients were also detected over several relatively small water bodies during cold (winter) season. The important finding is the positive trend of the land-sea LWP gradient detected within the time period 2011-2017. The analysis of intra-seasonal features revealed special conditions on the territory of the Gulf of Finland where in June and July large and moderate positive LWP gradients prevail over negative ones while in August positive and negative gradients are much smaller (in terms of absolute values) and occur with equal frequency. This result can lead to the conclusion about possible common physical mechanisms that drive the land-sea LWP difference in the Baltic Sea region at small distances from the coastline. The diurnal cycle of the LWP land-sea gradient has been detected in June and July while there was no evidence for it in August. For several specific cases, atmospheric parameters over the mesoscale domain comprising Gulf of Finland and several lakes have been simulated with the numerical model ICON in limited area and weather prediction mode.

Research paper thumbnail of Retrieval of the land-sea contrast of cloud liquid water path by applying a physical inversion algorithm to combined zenith and off-zenith ground-based microwave measurements

Combined zenith and off-zenith ground-based observations by modern microwave radiometers provide ... more Combined zenith and off-zenith ground-based observations by modern microwave radiometers provide an opportunity to study horizontal inhomogeneities of the humidity field in the troposphere and of the cloud liquid water path (LWP) spatial distribution. However, practical applications are difficult and require thorough analysis of the information content of measurements, assessment of errors of data processing algorithm and the development of the quality control procedures. In this study we analyse the application of our LWP retrieval algorithm based on the inversion of the radiative transfer equation to the problem of detection of the LWP horizontal inhomogeneities by means of ground-based microwave observations in the vicinity of a coastline of a water object of medium size. The study is based on data acquired by the microwave radiometer RPG-HATPRO which is located in the suburbs of St.Petersburg, Russia, at 2.5 km distance from the coastline of the Neva Bay (the Gulf of Finland) and is operating in angular scanning mode in the vertical plane. The retrieval setup is organised in such a way that zenith and off-zenith measurements provide equal sensitivity to atmospheric parameters. The optimal elevation angles for off-zenith observations are selected. The possibility to detect LWP horizontal inhomogeneity, namely the LWP land-sea contrast, for different measurement geometries (elevation angles) and values of cloud base height is analysed. It is shown that ground-based microwave observations in the vicinity of a coastline can be a valuable tool for validation of the space-borne measurements of the LWP land-sea contrast if three principal requirements are met: (a) the multi-parameter physical inversion method is used for retrieving LWP; (b) rigorous bias correction and quality control procedures are applied to the retrieval results; (c) the information on the cloud base height is available. As a result of processing the microwave measurements at the observational site of St.Petersburg State University, the monthlyaveraged values of the LWP land-sea difference have been obtained for summer months within the period 2013-2021. For 24 out of 25 months of high quality observations, the LWP land-sea monthly difference is positive (larger values over land and smaller values over water) and can reach 0.06-0.07 kg m-2. The estimations of the LWP land-sea contrast obtained from the ground-based microwave measurements at the observational site of St.Petersburg University are in very good agreement with the values of the LWP land-sea contrast obtained from the multi-year space-borne measurements by the SEVIRI instrument (Spinning Enhanced Visible and InfraRed Imager) in the region of the Neva Bay (the Gulf of Finland) in June

Research paper thumbnail of Inter-annual, seasonal and diurnal features of the cloud liquid water path over the land surface and various water bodies in Northern Europe as obtained from the satellite observations by the SEVIRI instrument in 2011–2017

. Liquid water path (LWP) is one of the most important cloud parameters. The knowledge on LWP is ... more . Liquid water path (LWP) is one of the most important cloud parameters. The knowledge on LWP is critical for many studies including global and regional climate modelling, weather forecasting, modelling of hydrological cycle and interactions between different components of the climate system: the atmosphere, the hydrosphere, and the land surface. Satellite observations by the SEVIRI and AVHRR instruments have already provided the evidences of the systematic difference between the LWP values derived over the land surface and over the Baltic Sea and major lakes in Northern Europe during both cold and warm seasons. The goal of the present study is to analyse the phenomenon of the LWP horizontal inhomogeneities in the vicinity of various water bodies in Northern Europe making focus on the temporal and spatial variation of LWP. The objects of investigation are water bodies and water areas located in Northern Europe which are different in size and other characteristics: Gulf of Finland, Gulf of Riga, the Neva River bay, lakes Ladoga, Onega, Peipus, Pihkva, Ilmen, and Saimaa. The input data are the LWP values of pure liquid-phase clouds derived from the space-borne observations by the SEVIRI instrument in 2011–2017 during daytime. The study revealed that in general the mean values of the land-sea LWP gradient are positive during all seasons (larger values over land, smaller values over water surface). However, the negative gradients were also detected over several relatively small water bodies during cold (winter) season. The important finding is the positive trend of the land-sea LWP gradient detected within the time period 2011–2017. The analysis of intra-seasonal features revealed special conditions on the territory of the Gulf of Finland where in June and July large and moderate positive LWP gradients prevail over negative ones while in August positive and negative gradients are much smaller (in terms of absolute values) and occur with equal frequency. This result can lead to the conclusion about possible common physical mechanisms that drive the land-sea LWP difference in the Baltic Sea region at small distances from the coastline. The diurnal cycle of the LWP land-sea gradient has been detected in June and July while there was no evidence for it in August. For several specific cases, atmospheric parameters over the mesoscale domain comprising Gulf of Finland and several lakes have been simulated with the numerical model ICON in limited area and weather prediction mode. These simulations have clearly demonstrated the LWP land-sea gradient and have pointed out less stability of the atmosphere over land surfaces.

Research paper thumbnail of Detection of the cloud liquid water path horizontal inhomogeneity in a coastline area by means of ground-based microwave observations: feasibility study

Atmospheric Measurement Techniques

Research paper thumbnail of The reply to the anonymous referee #2 (RC2)

Research paper thumbnail of The reply to the anonymous referee #1 (RC1)

Research paper thumbnail of Emission Monitoring Mobile Experiment (EMME): an overview and first results of the St. Petersburg megacity campaign-2019

results of the EMME observational campaign using the mass balance approach. The CO 2 emission flu... more results of the EMME observational campaign using the mass balance approach. The CO 2 emission flux for St. Petersburg as an area source was estimated to be 89 ± 28 kt km −2 yr −1 , which is 2 times higher than the corresponding value in the EDGAR database. The experiment revealed the CH 4 emission flux of 135 ± 68 t km −2 yr −1 , which is about 1 order of magnitude greater than the value reported by the official inventories of St. Petersburg emissions (∼ 25 t km −2 yr −1 for 2017). At the same time, for the urban territory of St. Petersburg, both the EMME experiment and the official inventories for 2017 give similar results for the CO anthropogenic flux (251 ± 104 t km −2 yr −1 vs. 410 t km −2 yr −1) and for the NO x anthropogenic flux (66 ± 28 t km −2 yr −1 vs. 69 t km −2 yr −1).

Research paper thumbnail of The Use of Linear Regression Relations Derived from Model and Experimental Data for Retrieval of the Water Content of Clouds from Ground-Based Microwave Measurements

Atmospheric and Oceanic Optics

Research paper thumbnail of Cross-comparison of cloud liquid water path derived from observations by two space-borne and one ground-based instrument in Northern Europe

Atmospheric Measurement Techniques Discussions

Cloud liquid water path (LWP) is one of the target atmospheric parameters retrieved remotely from... more Cloud liquid water path (LWP) is one of the target atmospheric parameters retrieved remotely from ground-based and space-borne platforms using different observation methods and processing algorithms. Validation of LWP retrievals is a complicated task since a cloud cover is characterised by strong temporal and spatial variability while remote sensing methods have different temporal and spatial resolution. An attempt has been made to compare and analyse the collocated LWP data delivered by two satellite instruments SEVIRI and AVHRR together with the data derived from microwave observations by the ground-based radiometer RPG-HATPRO. The geographical region of interest is the vicinity of St.Petersburg, Russia, where the RPG-HATPRO radiometer is operating. The study is focused on two problems. The first one is the so-called scale difference problem which originates from dissimilar spatial resolutions of measurements. The second problem refers to the land-sea LWP gradient. The radiometric site is located 2.5 km from the coastline where the effects of the LWP gradient are pronounced. A good agreement of data obtained at the microwave radiometer location by all three instruments (HATPRO, SEVIRI and AVHRR) during warm and cold seasons is demonstrated (the largest correlation coefficient 0.93 was detected for HATPRO and AVHRR data sets). The analysis showed no bias of the SEVIRI results with respect to HATPRO data and a high bias (0.013-0.017 kg m-2) of the AVHRR results for both warm and cold seasons. The analysis of LWP maps plotted on the basis of the SEVIRI and AVHRR measurements over land and water surfaces in the vicinity of St.Petersburg revealed the unexpectedly high LWP values delivered by AVHRR during cold season over the Neva river bay and over the Saimaa Lake and the abnormal land-sea LWP gradient in these areas. For the detailed evaluation of atmospheric state and ice cover in the considered geographical regions during the periods of ground-based and satellite measurements, reanalysis data were used. It is shown that the most probable reason for the observed artifacts in the AVHRR measurements over water/ice surfaces is the coarse resolution of the land-sea and snow/ice masks used by the AVHRR retrieval algorithm. The influence of a cloud field inhomogeneity on the agreement between the satellite and the groundbased data was studied. For this purpose, the simple estimate of the LWP temporal variability was used as a measure of the

Research paper thumbnail of Cloud liquid water path in the sub-Arctic region of Europe as derived from ground-based and space-borne remote observations

Atmospheric Measurement Techniques

Tropospheric clouds are a very important component of the climate system and the hydrological cyc... more Tropospheric clouds are a very important component of the climate system and the hydrological cycle in the Arctic and sub-Arctic. Liquid water path (LWP) is one of the key parameters of clouds urgently needed for a variety of studies, including the snow cover and climate modelling at northern latitudes. A joint analysis was made of the LWP values obtained from observations by the SEVIRI satellite instrument and from ground-based observations by the RPG-HATPRO microwave radiometer near St Petersburg, Russia (60 • N, 30 • E). The time period of selected data sets spans 2 years (December 2012-November 2014) excluding winter months, since the specific requirements for SEVIRI observations restrict measurements at northern latitudes in winter when the solar zenith angle is too large. The radiometer measurement site is located very close to the shore of the Gulf of Finland, and our study has revealed considerable differences between the LWP values obtained by SEVIRI over land and over water areas in the region under investigation. Therefore, special attention was paid to the analysis of the LWP spatial distributions derived from SEVIRI observations at scales from 15 to 150 km in the vicinity of St Petersburg. Good agreement between the daily median LWP values obtained from the SEVIRI and the RPG-HATPRO observations was shown: the rms difference was estimated at 0.016 kg m −2 for a warm season and 0.048 kg m −2 for a cold season. Over 7 months (February-May and August-October), the SEVIRI and the RPG-HATPRO instruments revealed similar diurnal variations in LWP, while considerable discrepancies between the diurnal variations obtained by the two instruments were detected in June and July. On the basis of reanalysis data, it was shown that the LWP diurnal cycles are characterised by considerable interannual variability.

Research paper thumbnail of Cross-validation of two liquid water path retrieval algorithms applied to ground-based microwave radiation measurements by the RPG-HATPRO instrument

International Journal of Remote Sensing

Research paper thumbnail of Quality assessment of integrated water vapour measurements at St. Petersburg site, Russia: FTIR vs. MW and GPS techniques

Atmospheric Measurement Techniques Discussions

The cross-comparison of different techniques for atmospheric integrated water vapour (IWV) measur... more The cross-comparison of different techniques for atmospheric integrated water vapour (IWV) measurements is the essential part of their quality assessment protocol. We inter-compare the synchronised data sets of IWV values measured by Fourier-transform infrared spectrometer Bruker 125 HR (FTIR), microwave radiometer RPG-HATPRO (MW) and global navigation satellite system receiver Novatel ProPak-V3 (GPS) at St. Petersburg site between August 2014 and October 2016. Generally, all three techniques agree well with each other and therefore are suitable for monitoring IWV values at St. Petersburg site. We show that GPS and MW data quality depends on the atmospheric conditions; in dry atmosphere (IWV smaller than 6 mm), these techniques are less reliable at St. Petersburg site than the FTIR method. We evaluate the upper bound of statistical measurement errors for clear-sky conditions as 0.33 ± 0.03 mm (2.0 ± 0.3 %), 0.54 ± 0.03&t...