Statistical Analysis of Cloud Cover at Pakistan Coastal Regions (original) (raw)
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Proceedings of 12th International Conference on Statistical Sciences, 2014
In this communication, we have presented the empirical assessment of the effects of atmospheric relative humidity on cloud cover at the Quetta region, Pakistan using dataset on a monthly basis from 1980 to 2009. Relative humidity is an important variable in the study of the atmospheric dynamics and ecosystem. Clouds are also one of the most significant constituents of our atmosphere. Clouds deliver water from the atmosphere to the Earth’s surface as rain or snow and are thus a key step in the hydrologic cycle. To study the behavior and association of relative humidity on cloud cover at the Quetta region, we have adopted approaches such as Exploratory Data Analysis (EDA). It has been observed that the relative humidity has a significant and positive correlation on cloud cover at the Quetta region. In order to strengthen our claim, we have compared the data sets of relative humidity with cloud cover at the Quetta region and analyzed both the data sets that exhibit positive correlation along with the interpretations.
Variation in Meteorological Parameters Over Pakistan during April 2014
Journal of Basic & Applied Sciences, 2017
In this study we investigated the meteorological data comprising temperature, dew point, humidity and mean sea level for four major cities of Pakistan (Karachi, Multan, Lahore and Peshawar) on varying latitudes from 25°N to 34°N. These cities are selected to study the variation of coastal, southern, central and northern parts of Pakistan and different variations are observed in ranges i.e difference between lowest and highest values. A clear variation in ranges of meteorological parameters are investigated for these cities to validate this research. This variation in meteorological parameters is because of climate change due to flow of high moisture laden winds from Arabian sea towards Karachi coast in the south. The results obtained regarding dew point temperature, moisture content and atmospheric pressure in the southern city of Karachi represent low values instead of high. As a result, Karachi has different climatic patterns as a coastal city than other areas which are continenta...
Correlation of Monthly Average Daily Global Solar Radiation with Cloudiness for Karachi , Pakistan
2012
For developing countries like Pakistan, the paucity of reliable solar radiation data necessitates the development of empirical models. To develop such a model one could use various parameters. In this study, linear regression models are developed to estimate the monthly average daily global radiation using cloudiness data for Karachi, Pakistan for the period of 20 years (1990-2010). The results showed that the models could estimate global radiation within acceptable error.
Variability of aerosol optical depth and their impact on cloud properties in Pakistan
Journal of Atmospheric and Solar-Terrestrial Physics, 2014
This study analyzes seasonal and temporal variations in aerosol optical depth (AOD), and the impact of these variations on the properties of clouds over five cities in Pakistan, using Moderate Resolution Imaging Spectroradiometer (MODIS) data, obtained from the Terra satellite during the period (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011). The obtained results indicated seasonal variation in AOD, with a high value of 2.3, in summer and low values of 0.2, in winter for the costal part of the region. The relationship between AOD and other cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud optical thickness (COT), cloud liquid water path (CLWP), cloud top temperature (CTT), and cloud top pressure (CTP) were analyzed. On a temporal scale, latitudinal variations of both WV and AOD produce high correlations (40.6) in some regions, and moderate correlations (0.4-0.6) in the other regions. An increasing trend in CF with AOD was found over urban regions in the period of observations. The CF values were higher for Lahore than the other selected regions during the whole period. During autumn and winter seasons the correlation was found to be positive between AOD and CLWP, while negative correlation was observed during the other seasons for all the selected regions. COT showed negative correlation with AOD at all locations except Karachi during spring and summer seasons.
Theoretical and Applied Climatology, 2017
The goal of the present study is to provide a climatic description of spatiotemporal variations of cloud fractions based on geographic characteristics over Iran during daytimes. Analyses are performed on the basis of 15 years of data collected from the MODIS instrument aboard Terra and Aqua satellites, data from 120 weather stations, ERA-Interim reanalysis, and geographic data (latitude, altitude, and vegetation cover). We have compared the consistency of MODIS monthly mean of cloud fractions aboard the Terra and Aqua with ERA-Interim and weather stations data. The results showed good agreement (R 2 = up to 74 %) between them but the data is more consistent during the cold months. Weather station data has a better overall agreement with MODIS compared to ERA-Interim. Temporal variations of cloud fraction showed maximum standard deviation in autumn for both satellite observations. Trend analyses applied to both data indicate nonsignificant trends for most months, although a significant decreasing trend of 2.2% per year during December and an increasing trend of 2.1% per year during May were observed. We found that the maximum and minimum monthly means of cloud fraction correspond to December to February (56 to 63%) and June-July-September (8 to 26%), respectively. Analysis of latitudinal forcing on cloud fraction showed that an increase in cloud fraction is coupled with an increase in latitude; this pattern is true only up to 31.5°N in summer. The reverse pattern is related to the Asian Monsoon system over Iran in low latitudes. Topographic forcing in this mountainous area often leads to orographic convection in the elevations of 500-1500 m during spring and autumn and coastal convection during summer. Vegetation also has a strong positive correlation with cloud fraction.
Aerosol and Air Quality Research, 2015
In this study, aerosols spatial, seasonal and temporal variations over Sindh, Pakistan were analyzed which can lead to variations in the microphysics of clouds as well. All cloud optical properties were analyzed using Moderate Resolution Imaging Spectroradiometer (MODIS) data for 12 years from 2001 to 2013. We also monitored origin and movements of air masses that bring aerosol particles and may be considered as the natural source of aerosol particles in the region. For this purpose, the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to make trajectories of these air masses from their sources. Aerosol optical depth (AOD) high values were observed in summer during the monsoon period (June-August). The highest AOD values in July were recorded ranges from 0.41 to 1.46. In addition, low AOD values were found in winter season (December-February) particularly in December, ranges from 0.16 to 0.69. We then analyzed the relationship between AOD and Ångström exponent that is a good indicator of the size of an aerosol particle. We further described the relationships of AOD and four cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP) by producing regional correlation maps of their data values. The analyses showed negative correlation between AOD and Ångström exponent especially in central and western Sindh. The correlation between AOD and WV was throughout positive with high correlation values > 0.74 in whole Sindh except eastern most arid strip of the Thar Desert in the region. The correlation between AOD and CF was positive in southern Sindh and goes to negative in northern Sindh. AOD showed a positive correlation with CTP and CTT in northern Sindh and a negative correlation in southern Sindh. All these correlations were observed to be dependent on the meteorological conditions for all of the ten sites investigated.
Advances in Space Research, 2010
Clouds are important elements in climatic processes and interactions between aerosols and clouds are therefore a hot topic for scientific research. Aerosols show both spatial and temporal variations, which can lead to variations in the microphysics of clouds. In this research, we have examined the spatial and temporal variations in aerosol particles over Pakistan and the impact of these variations on various optical properties of clouds, using Moderate Resolution Imaging Spectroradiometer (MODIS) data from the Terra satellite. We used the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model for trajectory analysis to reveal the origins of air masses, with the aim of understanding these spatial and temporal variabilities in aerosol concentrations. We also documented seasonal variations in patterns of aerosol optical depth (AOD) over Pakistan, for which the highest values occur during the monsoon season (June-August). We then analyzed the relationships between AOD and four other cloud parameters, namely water vapour (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP). Regional correlation maps and time series plots for aerosol (AOD) and cloud parameters were produced to provide a better understanding of aerosol-cloud interaction. The analyses showed strong positive correlations between AOD and WV for all of the eight cities investigated. The correlation between AOD and CF was positive for those cities where the air masses were predominantly humid, but negative for those cities where the air masses were relatively dry and carried a low aerosol abundance. These correlations were clearly dependent on the meteorological conditions for all of the eight cities investigated. Because of the observed AOD-CF relationship, the co-variation of AOD with CTP and CTT may be attributable to largescale meteorological variations: AOD showed a positive correlation with CTP and CTT in northern regions of Pakistan and a negative correlation in southern regions.
Routine, Extreme and Engineering Meteorology Analysis for Karachi Coastal Area
Earth Science Malaysia, 2020
Pakistan’s largest city, Karachi, which is industrial centre and economic hub needs focus in research and development of every field of Engineering, Science and Technology. Urbanization and industrialization is resulting bad weather conditions which prolongs until a climate change. Since, Meteorology serves as interdisciplinary field of study, an analytical study of real and region-specific meteorological data is conducted which focuses on routine, extreme and engineering meteorology of metropolitan city Karachi. Results of study endorse the meteorological parameters relationship and establish the variability of those parameters for Karachi Coastal Area. The rise of temperature, decreasing trend of atmospheric pressure, increment in precipitation and fall in relative humidity depict the effects of urbanization and industrialization. The recorded extreme maximum temperature of 45.50C (on June 11, 1988) and the extreme minimum temperature of 4.5 0C(on January 1, 2007) is observed at K...
Precipitation rate climatology related to different cloud types using satellite imagery over Iran
Arabian Journal of Geosciences, 2018
Cloud types have a substantial influence on precipitation. This paper presents a study of the monthly variations of daytime different cloud types over Iran using data collected from Moderate-resolution Imaging Spectroradiometer (MODIS) aboard Terra during 2001-2015, MODIS aboard Aqua during 2002-2015, International Satellite Cloud Climatology Project (ISCCP) H-series cloud type data during 2001-2009 and precipitation rate associated with different cloud types using Tropical Rainfall Measuring Mission (TRMM) satellite products during 2001-2009. Different cloud types were determined using MODIS cloud optical thickness and cloud top pressure data based on ISCCP algorithm. The results showed that stratocumulus and cumulus clouds have maximum occurrence frequency over marine areas especially southern seas. The maximum frequency of nimbostratus and deep convective occurrence occurred over mountainous regions particularly at the time of Aqua overpass and cirrus and cirrostratus are observed over southeast of Iran during warm months due to monsoon system. Altostratus cloud is extended in each month except January, at the time of Terra overpass while nimbostratus is seen at the time of Aqua overpass during warm months in the study area. Cumulus and altocumulus clouds have shown remarkable frequency in all months especially over marine regions during warm and fall months. The higher value of precipitation rate is related to altostratus with a rate approximately 7 mm/h at the time of Terra overpass during April. Altostratus has the maximum recorded precipitation rate except in Nov., Dec., Sep., and Jan. at the time of Terra overpass, whereas the maximum precipitation rate is linked to nimbostratus cloud activity (up to 5 mm/h) except for March, April, and Sep. at the time of Aqua overpass. Deep convective (up to 1. 32 mm/h), cirrostratus (up to 1.11 mm/h), and cirrus (0.02 mm/h) are observed only in warm months. The results were compared with ISCCP cloud types so that precipitation rate classified from low to high and Spearman rank correlation was calculated. The results showed good agreement between these two cloud type data; however, there were few notable difference between them.
A Study on the Classification of Clouds Using Time Variation of the Amount of Solar Radiation
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 2016
Bunkyo cho-3, Matsuyama shi, Ehime, Japan The classification of clouds and its spatial and temporal variation is important to understand the concept of local climate. Thus, this study was carried out to explore the potential for using the statistical analysis (standard deviation) of time series of one hour averaged pyranometer observation to determine the types of clouds in the Matsuyama plain. Instruments were installed at 6 observation points covering the entire study area. Clear sky rate was considered as an index to identify the reduction in the solar radiation due to presence of cloud. The development of high raised cloud such as cirrostratus and cumulus were observed with small and large time standard deviation respectively and clear sky rate between 0.4-0.6. Also, the formation of cloud were observed to be high in the urban area and the inland area. This was further verified using the whole sky images taken by the camera installed at Ehime University. The results would be beneficial for the study of the rainfall pattern in different part of Matsuyama plain and to understand the effect of urbanization on the local climate.