Characterization of the atmospheric boundary layer from radiosonde observations along eastern end of monsoon trough of India (original) (raw)
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Some Atmospheric Boundary Layer Characteristics over north India
The structure, evolution and behavior of atmospheric boundary layer (ABL) is largely regulated by topography, land-surface characteristics, atmospheric radiation and synoptic conditions. Therefore, the mesoscale models like Weather Research Forecasting (WRF) are better suited for ABL studies. This book emphasizes upon the ABL characteristics over north Indian region during two contrasting synoptic situations of summer and winter. First chapter is introductory in nature. A brief description about the WRF modeling system is given in the second chapter. Third chapter describes about the study of regional scale boundary layer characteristics over north India. In chapter four, consequences of sensitivity experiments with different land-surface and boundary layer parameterization schemes are presented. To investigate the influence of finer resolution on the boundary layer characteristics, two-way nesting technique is implemented in the study described in fifth chapter by keeping the parent domain intact and the child domains configured with 5 km resolution over the three cities Delhi, Ahmedabad and Jodhpur.
Pure and Applied Geophysics, 2007
The diurnal structure of the boundary layer during Indian summer monsoon period is studied using a one-dimensional meteorological boundary layer model and the observations collected from the Monsoon Trough Boundary Layer Experiment conducted in 1990 at Jodhpur, India. The model was initialized with the observed temperature profiles at 0530 LST on 17 July, 1990 at Jodhpur and was run for 26 hours. The study is carried out with a geostrophic wind speed of 9.5 m s)1 corresponding to the strong wind simulation. The mean thermodynamic and wind structure simulated by the model are in good agreement with those observed from 30 m tower. The computed surface layer characteristics such as the surface fluxes, TKE and standard deviations of velocity components are found to be reasonably in good agreement with those based on turbulence measurements. The shear and buoyancy budget computed from the model are also compared with the turbulence measurements. The integrated cooling budget in the nocturnal boundary layer is examined.
Evaluation of the boundary layer depth in semi-arid region of India
Dynamics of Atmospheres and Oceans, 2010
The annual variation in Planetary Boundary Layer (PBL) height is determined from the profiles of conserved thermodynamic variables, i.e. virtual potential temperature  v , equivalent potential temperature  e and saturated equivalent potential temperature  es , using radiosonde data at Anand (23 • 35 N, 72 • 55 E, 45.1 m a.s.l.), India. Out of all the variables, the  v profile seems to provide the most reasonable estimate of the PBL height. This has been supplemented by T-Phi gram analysis for specific days. The analysis has been done for 00, 03, 06, 09 and 12 GMT for the 14th and 15th day of each month in the year 1997 based on LASPEX-97 data. In winters the height of boundary layer is very low due to subsidence and radiation cooling while heights in pre-monsoon months exhibit large variations.
Advances in Meteorology, 2011
Vertical profiles of meteorological parameters obtained from balloon-borne GPS Radiosonde for a period of more than two years are analyzed for characterization of the coastal atmospheric boundary layer (CABL) over Thumba (, , India). The study reports seasonal variability in the thickness of three different sublayers of the CABL, namely, mixed layer, turbulent flow, and sea breeze flow. Among the three, the vertical thickness of sea breeze flow showed considerable dominance on the other two throughout the year. Mixed layer heights derived through gradients in virtual potential temperature () showed large seasonal variability with a peak in the Summer and Post-Monsoon. On the other hand, the vertical thickness of turbulent flow remained steady all through the year. Results from the present study indicate that the magnitudes of mixed layer heights are often larger than the turbulent flow thickness.
The local weather and air quality over a region are greatly influenced by the atmospheric boundary layer (ABL) structure and dynamics. ABL characteristics were measured using a tethered balloon-sonde system over Kharagpur (22.32◦N, 87.32◦E, 40m above MSL), India, for the period 7 December 2004 to 30 December 2004, as a part of the Indian Space Research Organization– Geosphere Biosphere Program (ISRO–GBP) Aerosol Land Campaign II. High-resolution data of pressure, temperature, humidity, wind speed and wind direction were archived along with surface layer measurements using an automatic weather station. This paper presents the features of ABL, like ABL depth and nocturnal boundary layer (NBL) depth. The sea surface winds from Quikscat over the oceanic regions near the experiment site were analyzed along with the NCEP/NCAR reanalysis winds over Kharagpur to estimate the convergence of wind, moisture and vorticity to understand the observed variations in wind speed and relative humidity, and also the increased aerosol concentrations. The variation of ventilation coefficient (V C), a factor determining the air pollution potential over a region, is also discussed in detail.
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Atmospheric Environment. Part A. General Topics
Characteristic variations in the thermodynamic parameters of the atmospheric boundary layer at Pune (18°32'N, 73°51'E, 559 m a.s.l.) have been studied using the aerological observations collected during the summer monsoon seasons of 1980 and 1981, and temperature observations from aircraft during the summer monsoons of 1976, 1979-1981. This study showed suppression of the mixed layer, absence of inversion/stable layers and decreased convective instability in the lower layers during the period of active monsoon conditions. The reverse was observed during the periods of weak/break monsoon conditions. Temperature stratification of sub-cloud layer has been classified into four different categories depending on the extent of the mixed layer and the gradient of potential temperature in the overlying stable layer. It was observed that these categories cover all types of weather conditions which prevailed during the monsoon season. The results are discussed with the possible association of the weather conditions prevailed during'the active and break monsoon periods.
Boundary-Layer Meteorology, 2000
An attempt is made to study the planetary boundary layer (PBL) characteristics during the winter period at Anand (22.4 • N, 72.6 • E), a semi-arid region, which is located in the western part of India. A one-dimensional turbulent kinetic energy (TKE) closure model is used for the study. The structure of the PBL, which consists of profiles of zonal and meridional components of wind, potential temperature and specific humidity, is simulated. A one-dimensional soil heat and moisture transport parameterization scheme is incorporated for the accurate representation of the energy exchange processes at the soil-atmosphere interface. The diurnal variation of fluxes of sensible heat, latent heat, shortwave radiation, net radiation and soil flux, soil temperature at different depths, Richardson number and TKE at the height of the constant flux layer is studied. The model predictions are compared with the available observations obtained from a special Land Surface Processes (LSP) experiment.
Atmospheric Research, 2012
Spatial and temporal variabilities in the vertical structure of Marine Atmospheric Boundary Layer (MABL) over the Bay of Bengal (BoB) are investigated through a ship-borne field experiment measurements pertaining to three different classes, namely: night, morning and afternoon conditions. High-resolution vertical profiles of meteorological parameters obtained through balloon-borne GPS Sondes during the Winter phase of Integrated Campaign for Aerosols, gases and Radiation Budget (W-ICARB) formed the primary database for the present investigation. The study advocates usage of wind shear profiles in association with virtual potential temperature (θ v) and specific humidity (q) profiles for determination of the mixed layer heights (MLH). The mean values of turbulent flow thickness (TFT) obtained from the vertical profiles of Bulk Richardson Number (Ri B) and MLH magnitudes for the entire cruise did not show any appreciable variations for three classes. During the entire cruise period, the MLH varied in a range from 450 m to 1500 m with a mean of about 900 m, whereas the TFT variations were confined between 125 m and 1475 m with a mean of about 581 m. The statistical means of TFT and MLH were similar for nighttime profiles, whereas they showed significant differences in the morning and afternoon conditions. Spatio-temporal variability in the MLH showed good correlation with the surface-layer sensible heat flux which is one of the driving mechanisms in mixing processes.