scholarly journals Estimation of divergent wind from OLR data for use in objective analysis over the Indian region

MAUSAM ◽  
2021 ◽  
Vol 44 (1) ◽  
pp. 77-84
Author(s):  
P. L. KULKARNI ◽  
D. R. TALWALKAR ◽  
S. NAIR
Keyword(s):  
Vertical Velocity ◽  
Wind Field ◽  
Empirical Relation ◽  
Initial Guess ◽  
Indian Region ◽  
Divergent Part ◽  
Free Region ◽  
Synoptic Conditions ◽  
Cloudy Region ◽  
Cloud Top Temperature

A scheme is formulated for the use of OLR data in the estimation of vertical velocity; divergence and then the divergent part of the wind over Indian region. In this scheme, ascending motion over cloudy region is estimated from an empirical relation between the cloud top temperature and descending motion over cloud-free region is estimated from the thermodynamic energy equation and both are blended. From this blended vertical velocity field, aivergence, velocity potential and divergent winds at all standard levels from 4 to 8 July 1979 at 00 UTC are computed. These fields are compared with satellite cloud pictures, rainfall etc and they are found to be realistic in depicting the synoptic conditions. Total wind is computed as the sum of the estimated divergent component and rotational component computed from observed wind field. For assessment of the scheme, this total wind field at 850 hPa is used as initial. guess field in univariate optimum interpolation scheme and analyses were made for the period 4 to 8 July 1979. Results show that scheme is able to produce realistic analyses which included divergent part of the wind.

Description of Wind Field Dynamic Patterns in a Valley and Their Relation to Mesoscale and Synoptic-Scale Meteorological Situations

1995 ◽  
Vol 34 (1) ◽  
pp. 49-67 ◽  
Author(s):  
R. Guardans ◽  
I. Palomino
Keyword(s):  
Wind Field ◽  
Transition Probabilities ◽  
Meteorological Data ◽  
Atmospheric Dispersion ◽  
Synoptic Situation ◽  
Large Set ◽  
Valley Wind ◽  
Complete Collection ◽  
Emergency Plans ◽  
Synoptic Conditions

Abstract A large set of hourly meteorological data from seven towers deployed in Montesina Valley (Cordoba, Spain) is studied in relation to the prevailing synoptic situation. The complete collection of daily synoptic maps for 1985-90 has been classified in seven basic weather patterns. First-order transition probabilities and weatherpattern persistences have been calculated for each of the patterns. The behavior of the local valley wind field is described as a function of the synoptic patterns. The work reported here, based on observations of the characteristic time and space patterns of flow in the valley under different synoptic conditions, has made it possible to obtain a set of empirical rules and regression functions to produce forecasts of the local wind field as a function of the synoptic situation and the hour of the day to be used in the emergency plans. The result of this work is currently being implemented in an atmospheric dispersion module of an expert system that will be used as a tool to predict the evolution of accidental and routine hazardous emissions to the atmosphere in complex terrain such as valleys and coastal areas.

scholarly journals Bora-induced currents corresponding to different synoptic conditions above the Adriatic

2005 ◽  
Vol 23 (4) ◽  
pp. 1083-1091 ◽  
Author(s):  
G. Beg Paklar ◽  
A. Bajić ◽  
V. Dadić ◽  
B. Grbec ◽  
M. Orlić
Keyword(s):  
Numerical Model ◽  
Wind Field ◽  
High Speed ◽  
Western Mediterranean ◽  
First Episode ◽  
Surface Currents ◽  
Po River ◽  
Northern Adriatic ◽  
Synoptic Conditions ◽  
Bora Wind

Abstract. The Bora wind field is characterised by strong vorticity and divergence. Several numerical experiments, in which an oceanographic model was forced with northeasterly winds having climatological alongshore variability, were performed in order to study the influence of spatial variability in the bora wind field on the surface currents in the northern Adriatic. Numerical model results showed that during bora episodes with lower speeds and fast offshore decay surface currents along transect Rovinj - Po River are predominantly in the downwind direction. On the other hand, during bora episodes with strong intensity and slow offshore decay, a cyclonic gyre due to the pronounced bora alongshore variability is formed in the northernmost part of the Adriatic Sea and the studied transect is influenced by the counter currents. Moreover, bora having a high speed and a short offshore range produces the same effect in the eastern part of the Rovinj - Po River transect as low-speed bora characterised by slow offshore decay. Eulerian current measurements performed in the northern Adriatic during bora episodes characterised by different synoptic conditions supported the numerical model findings. Surface currents during the bora episode of 8-11 February 1984 were directed downwind, whereas during the episode of 12-19 February 1984 they were directed upwind. The first episode was characterised by a deep bora layer with cyclonic activity over the western Mediterranean and Genoa Bay, whereas the second one was accompanied by temperature inversion and a southwesterly tropospheric wind above a shallow bora layer. According to the hydraulic theory developed by Smith (1985), an observed descent of isentropes during the second bora episode led to the stronger acceleration in the bora layer and its larger offshore extent. Different offshore bora decays during studied events were confirmed by a comparison of the wind data originating from the meteorological stations positioned on the opposite Adriatic coasts.

Impact of Monex-79 data on the objective analysis of the wind field over the Indian region

1982 ◽  
Vol 120 (3) ◽  
pp. 422-436 ◽  
Author(s):  
S. Rajamani ◽  
D. R. Talwalkar ◽  
P. U. Upasani ◽  
D. R. Sikka
Keyword(s):  
Wind Field ◽  
Indian Region ◽  
Objective Analysis

scholarly journals Temperature sounding of the atmosphere over the Indian region using satellite data

MAUSAM ◽  
2022 ◽  
Vol 44 (2) ◽  
pp. 167-174
Author(s):  
P.N. KHANNA ◽  
R.R. KELKAR
Keyword(s):  
Meteorological Data ◽  
Analysis Data ◽  
Initial Guess ◽  
Indian Region ◽  
Radiosonde Data ◽  
Retrieval Algorithm ◽  
New Delhi ◽  
University Of Wisconsin ◽  
Different Seasons ◽  
Using Data

Capability has been developed at the INSAT Meteorological Data Utilisation Centre (MDUC). New Delhi for making sounding retrievals using data from the U.S. Polar Orbiting Satellites; The International TOYS Processing Package (ITPP) developed by the University of Wisconsin, USA, was used for asking temperature soundings software for front-end processing and input of 1000 hPa analysis data Into the retrieval algorithm was developed at MDUC. In the physical retrieval method regression estimates generated listing stratospheric level HIRS channels and MSU channels were used as Initial guess. For the surface, two options were used, (i) climatological guess, and (ii) 1000 hPa analysis.   The paper discusses temperature retrievals over the Indian region made on 13 selected dates from different seasons in 1989-91. Results of comparison of satellite retrievals with colocated radiosonde data are presented.  There is good agreement between the two from 700 hPa to 150 hPa levels, with RMSE with 3 C. The error is higher at 850 hPa and near the surface, when climatologic IS used as surface guess, but IS within 3°-4° C when the 1000 hPa analysis is used.

scholarly journals Comparison of Thunderstorm Simulations from WRF-NMM and WRF-ARW Models over East Indian Region

2012 ◽  
Vol 2012 ◽  
pp. 1-20 ◽  
Author(s):  
A. J. Litta ◽  
Sumam Mary Ididcula ◽  
U. C. Mohanty ◽  
S. Kiran Prasad
Keyword(s):  
Indian Region ◽  
Squall Line ◽  
Severe Thunderstorm ◽  
East Indian ◽  
Weather Events ◽  
Arw Model ◽  
High Impact Weather ◽  
Activity Comparison ◽  
Cloud Top Temperature ◽  
Better Than

The thunderstorms are typical mesoscale systems dominated by intense convection. Mesoscale models are essential for the accurate prediction of such high-impact weather events. In the present study, an attempt has been made to compare the simulated results of three thunderstorm events using NMM and ARW model core of WRF system and validated the model results with observations. Both models performed well in capturing stability indices which are indicators of severe convective activity. Comparison of model-simulated radar reflectivity imageries with observations revealed that NMM model has simulated well the propagation of the squall line, while the squall line movement was slow in ARW. From the model-simulated spatial plots of cloud top temperature, we can see that NMM model has better captured the genesis, intensification, and propagation of thunder squall than ARW model. The statistical analysis of rainfall indicates the better performance of NMM than ARW. Comparison of model-simulated thunderstorm affected parameters with that of the observed showed that NMM has performed better than ARW in capturing the sharp rise in humidity and drop in temperature. This suggests that NMM model has the potential to provide unique and valuable information for severe thunderstorm forecasters over east Indian region.

Objective Calculations of Divergence, Vertical Velocity and Vorticity

1949 ◽  
Vol 30 (2) ◽  
pp. 45-49 ◽  
Author(s):  
John C. Bellamy
Keyword(s):  
Vertical Velocity ◽  
Wind Field

Methods of calculating horizontal divergence, vertical velocity and vorticity directly from wind observations without analyzing the wind field are presented. The appropriate formulae for these quantities in terms of the finite areas or volumes determined by the observation points are derived. Convenient nomographs and tabular forms for their calculation are described and illustrated.

Atmospheric Turbulence Encountered by High-Speed Ground Transport Vehicles

1977 ◽  
Vol 19 (5) ◽  
pp. 227-235 ◽  
Author(s):  
L. A. Balzer
Keyword(s):  
Atmospheric Turbulence ◽  
Vertical Velocity ◽  
Wind Field ◽  
High Speed ◽  
Statistical Properties ◽  
Arbitrary Orientation ◽  
Turbulent Wind ◽  
Transport Vehicle ◽  
Turbulent Wind Field

The structure of atmospheric turbulence near the ground is reviewed and the statistical properties of the longitudinal, lateral and vertical velocity components of the wind presented. The statistical properties of the turbulence encountered by a high-speed ground transport vehicle travelling through a turbulent wind field of arbitrary orientation are derived. Next, the statistical properties of the atmospheric forces acting on the vehicle are determined and a method of taking account of finite vehicle length is presented. The resulting formulae are applied to a typical tracked hovercraft vehicle.

scholarly journals An Effective Method for Detecting Clouds in GaoFen-4 Images of Coastal Zones

2020 ◽  
Vol 12 (18) ◽  
pp. 3003
Author(s):  
Zheng Wang ◽  
Jun Du ◽  
Junshi Xia ◽  
Cheng Chen ◽  
Qun Zeng ◽  
...  
Keyword(s):  
Satellite Images ◽  
Clustering Algorithm ◽  
Detection Method ◽  
Radiation Budget ◽  
Detection Methods ◽  
Coastal Zones ◽  
Cloud Detection ◽  
Free Region ◽  
Wide Range ◽  
Cloudy Region

Cloud-cover information is important for a wide range of scientific studies, such as the studies on water supply, climate change, earth energy budget, etc. In remote sensing, correct detection of clouds plays a crucial role in deriving the physical properties associated with clouds that exert a significant impact on the radiation budget of planet earth. Although the traditional cloud detection methods have generally performed well, these methods were usually developed specifically for particular sensors in a particular region with a particular underlying surface (e.g., land, water, vegetation, and man-made objects). Coastal regions are known to have a variety of underlying surfaces, which represent a major challenge in cloud detection. Therefore, there is an urgent requirement for developing a cloud detection method that could be applied to a variety of sensors, situations, and underlying surfaces. In the present study, a cloud detection method based on spatial and spectral uniformity of clouds was developed. In addition to having a spatially uniform texture, a spectrally approximate value was also present between the blue and green bands of the cloud region. The blue and green channel data appeared more uniform over the cloudy region, i.e., the entropy of the cloudy region was lower than that of the cloud-free region. On the basis of this difference in entropy, it would be possible to categorize the satellite images into cloud region images and cloud-free region images. Furthermore, the performance of the proposed method was validated by applying it to the data from various sensors across the coastal zone of the South China Sea. The experimental results demonstrated that compared to the existing operational algorithms, EN-clustering exhibited higher accuracy and scalability, and also performed robustly regardless of the spatial resolution of the different satellite images. It is concluded that the EN-clustering algorithm proposed in the present study is applicable to different sensors, different underlying surfaces, and different regions, with the support of NDSI and NDBI indices to remove the interference information from snow, ice, and man-made objects.

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