bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multifeature classification based rainfall estimation using visible infrared TRMM data
Authors: PAL P. K. , KISHTAWAL C. M. , AGARWAL NEERAJ 
Published: January 2022

In this study an attempt has been made to estimate the rain potential of clouds using the signatures in visible and infrared spectral channels by multi spectral classification approach. The data for this study was obtained from Visible Infrared Scanner (VIRS) and TRMM Microwave Instrument (TMI) onboard Tropical Rainfall Measuring Mission (TRMM) satellite. Fifteen VIRS derived parameters have been used for classification and the clouds were separated into 24 classes using K-Mean classification algorithm. Six out of these 24 classes were found to have high raining probability as well as high cumulative contribution to the total rainfall (~80%). A regression analysis has been performed to explain the TMI rainfall rate in terms of features derived from VIRS observations for these six classes. The results of classification and verification have been discussed.
Rainfall estimation using spaceborne microwave radar and radiometric measurements
Authors: GAIROLA R. M. , VARMA A. K. , AGARWAL VIJAY  K. 
Published: January 2022

The present paper deals with some of the recent remote sensing techniques for the estimation of rainfall, mainly from passive and active microwave measurements from space. The sensitivity analysis based on forward approach following the radiative transfer modelling using data from ECMWF and mesoscale models is presented. The inverse methods of retrieving rainfall from satellite microwave measurements mainly from the multiple regression and neural networks are presented based on the sensitivity analysis. The simulations are carried out for the multichannel measurements from TRMM-TMI, DMSP-SSM/I and Indian IRS-P4-MSMR radiometric channels and are assessed with the actual observations thereof. A few examples of the rainfall patterns are described and compared with some of the standard products from TRMM radiometer and radar. The examples of monthly rain rates derived from MSMR, are also shown qualitatively and quantitatively, for a typical monsoon month of August for brevity out of three consecutive years of analysis. Though the status of rainfall estimation presented is not exhaustive one, it is presented in view of the preparedness for the future missions like, Megha-Tropiques and Global Precipitation Mission.
Space based techniques for remote sensing of oceanic winds : A Review
Authors: SARKAR ABHIJIT 
Published: January 2022

Observations of surface winds over the global oceans at regular intervals from space platforms have been demonstrated. This paper focuses on different techniques developed over the past few decades. The most successful wind sensor has been the microwave scatterometer, which can provide vector winds with reasonable accuracy. With the launch of METOP-1, scheduled in 2005, scatterometer will be part of routine satellite system for weather forecast. Among the research efforts has been retrieval of winds from Synthetic Aperture Radar data, available in high spatial resolution and in both open oceans and coastal waters. Radiometric, altimetric and optical wind measuring techniques are also reviewed in the paper.
Conditions leading to monsoon onset over Kerala and the associated Hadley cell
Authors: JOSEPH P. V. , SOORAJ K. P. , RAJAN C. K. 
Published: January 2022

Monsoon onset over Kerala (MOK) is an important event in relation to the Asian Summer Monsoon and the global atmosphere and Ocean. It marks the beginning of an intense and large convective heat source north of the equator over the tropical Indian and west Pacific oceans and an intense low level jet stream that feeds moisture to the heat source, both having a life span of about 100 days from MOK. Using satellite data we are now able to monitor the slow evolution of this heat source which first forms near the equator over an area with large SST gradient (in the south-north direction) and slowly moves towards the warm pool over the southeast Arabian Sea.

A Monsoon Hadley cell (MHC) is associated with this large convective heat source which is particularly strong over the south-east Arabian Sea at MOK. The ascending branch of the MHC is over this heat source and its descending branch is over the subtropical south Indian ocean. The low level branch of the MHC called V850 is a strong meridional southerly flow at 850 hPa crossing the equator between the longitudes 35° E and 55° E. The upper level branch V200 is a meridional northerly flow at 200 hPa over the south Indian ocean between longitudes 45° E and 75° E. The intensity of the MCH taken as (V850 -V200) is found to increase rapidly during the 10 day period prior to MOK.
Impact of ATOVS temperature and moisture profiles on NCMRWF analysis and prediction
Authors: GUPTA M. DAS , MITRA A. K. , PRASAD V. S. , RAJAN D. 
Published: January 2022

Global high resolution (120 km) ATOVS temperature and moisture profile data from polar orbiting satellites NOAA 15 & 16 is been made available to user community recently by NESDIS (National Environmental Satellite, Data and Information Service). NCMRWF also has started using these products in its operational global data assimilation system. Extensive impact assessment experiments have been conducted prior to its operational utilization. Impact is also studied during the onset phase of southwest monsoon over India. Results of these experiments are presented in this article. Study show that the impact of ATOVS data is seen on the mean analysed and predicted fields upto 120 hrs prediction specially over the oceanic region. It also reveals that the utilization of these data is able to predict the rainfall over the Indian peninsular region and the adjoining ocean in more realistic manner upto 72 hr forecast, beyond which there is hardly any meaningful improvement.
Evapotranspiration estimation using remote sensing data
Authors: SINGH D. , HERLIN I. , BERROIR J. P. , BOUZIDI S. , LAHOCHE F. 
Published: January 2022

Evapotranspiration (ET) is a critical hydrological link between the earth surface and the atmosphere. It is therefore important point of issues involving many aspects of climate, climate change, and ecosystem response. It is well known that ET is the process responsible for the transfer of the moisture from soil and vegetated surface to the atmosphere. Changes in ET are likely to have large impacts on terrestrial vegetation. Since the distribution and abundance of plant communities are controlled to a large extent by the quantity and seasonality of moisture. If the changes in water balance are significant, major shifts in vegetative patterns and condition are a likely result of climate change. Equally changes in ET are likely to impact atmospheric composition of green house gases, and climate, as the hydrological cycle increases in intensity with warming. Therefore, in this paper, it is attempted to estimate the ET over vegetative and bare field using National Oceanic and Atmospheric Administration (NOAA)/ Advanced Very High Resolution Radiometer (AVHRR) data at coarse spatial resolution of 1.1 km as a function of Normalized Difference Vegetation Index (NDVI) and with semi-empirical approach. For this purpose, a model has been proposed to estimate the ET over vegetative and bare field. The dependence of ET on NDVI-Surface temperature has been checked by multiple regression analysis and quite good percentage of dependence of ET on NDVI-Surface temperature has been observed. This type of estimation will be helpful for climate modeler, climatologists, ecosystem modeler and regional planer.
Association between mid-latitude circulation and onset of Indian summer monsoon over Kerala
Authors: BHATLA R. , CHATTOPADHYAY J. 
Published: January 2022

Teleconnections between mid latitude circulation over different sectors and onset of Indian summer monsoon over Kerala for the period of 1971-89 have been examined. Significant negative relationships are observed between the meridional circulation indices and general perturbation of zonal flow and the monsoon onset over Kerala. Strong and significant positive relationships are also observed between frequency of zonal index over sector 160° E to 45° W and onset dates of monsoon over Kerala.
Evaluation of dynamical and thermal anomalies associated with the summer monsoon of 1997 and 1999
Authors: BHOWMIK S. K.ROY 
Published: January 2022

The year 1997 was characterized by rapid development of a strong El Nino event and during 1999, a La Nina episode prevailed. The response of all India monsoon rainfall to these events in 1997 (above normal rainfall; >100%) and 1999 (below normal rainfall; <100%) was of unusual nature. In this paper, the reasons for this have been investigated in terms of planetary scale dynamical and thermal anomaly indices. The major findings of this study are (a) The early onset of south west monsoon in 1999 was associated with the stronger positive vertical shear of zonal anomaly over the north Indian Ocean, (b) Development of an active inverse Hadley circulation over Indian longitude appears to play an important role to reactivate monsoon during August and September in 1997, (c) Positive anomalies of tropospheric temperature occupied larger area over the Tibetan Plateau in May 1999, (d) The geopotential height anomaly at 200 hPa over the Tibetan Plateau during the month of May in 1999, in the year of early onset, was considerably higher compared to 1997 and (e) The dominance of negative anomalies of mean sea level pressure during May in 1999 over Indian region reflected the La Nina influence.
A case study of katabatic winds over Schirmacher Oasis, east Antarctica
Authors: KULANDAIVELU E. , DANG S. P. 
Published: January 2022

Katabatic winds are a regular feature during night and early morning hours over valleys and low lying areas adjacent to high terrains. In Antarctica, the mass of the earth in the form of plateau is covered with full of ice and has a downslope from the South Pole everyside upto the coast. Due to cooling of air near the ground as well as due to pressure gradient, the coastal belt often experiences strong winds blowing down the slope of the plateau. In this study “katabatic wind” at Maitri over Schirmacher Oasis has been examined using the data collected during the 9th Indian Antarctic Expedition 1990-91. The primary results show that katabatic winds are observed in all the months with higher frequency and strength in winter compared to other seasons. A distinction between pure katabatic wind and extraordinary katabatic wind is done based on the wind direction and associated changes in the surface temperature and weather conditions.
Irrigation requirements of cotton at different agroclimatic regions of the country
Authors: CHATTOPADHYAY N. , SAMUI R. P. 
Published: January 2022

Studies were made to find out the irrigation requirements of different varieties of cotton grown at six locations situated in different agroclimatic regions of the country. It is found that there is a considerable variation of irrigation requirements at different growth stages of the crop and also among the varieties cultivated at different regions. In general, the crop requires maximum irrigation either at flowering or boll formation stages. The study reveals that more irrigation is required for the crop grown at Bellary (54.2-56.2 cm), Anand (45.4-63.4 cm) and Kovilpatti (41.0-63.4 cm) compared to that at Akola (15.0-47.3 cm) and Coimbatore (16.9-36.4 cm). Irrigation timing differs considerably due to high degree of variability of rainfall in different regions. Based on probability of rainfall at 70% level, irrigation requirements of cotton has been computed. Specific guidelines are generated to utilise the information for irrigation scheduling of cotton operationally through Agromet Advisory Service.
Systematic errors of IMD Operational NWP model
Authors: ROY BHOWMIK S. K. 
Published: January 2022

The systematic errors of IMD (India Meteorological Department) limited area model over Indian region using 48 hours forecast fields for winter and summer seasons are examined in this paper. The study reveals that the core of the sub tropical westerly jet and tropical easterly jet are well simulated in the zonal component of wind. In case of meridional component of wind significant difference is noticed between forecast and analysis. In the upper tropospheric levels (above 100 hPa) northerly biases are noticed. Thermal structure of the model exhibits cool bias in middle and lower tropospheric levels over the northern latitudes. The nature of model biases of the geopotential height changes with the season. Model drying over the tropical belt and moistening towards the northern latitudes are found in all the seasons studied.
On nowcasting wind shear induced turbulence over Chennai air field
Authors: SURESH R. 
Published: January 2022

With the newly installed Doppler Weather Radar at Cyclone Detection Radar station, Chennai during October 2001, it has been made possible to analyse the meteorological conditions conducive for the wind shear induced turbulence experienced by the pilots in the approach runway at the time of landing and take-off. The radar has been put into operation w.e.f. 21 February, 2002. Wind shears reported during February – October 2002, have been critically analysed in this study. The three dimensional shear (3DS), a combination of radial, azimuthal and elevation shears, gives a first hand information atleast half an hour before the occurrence of shear induced moderate turbulence when its value exceeds 16mps/km. The 3DS of more than 20mps/km is normally associated with turbulence experienced by the pilots. With the availability of sophisticated and vast computing power, it is now possible to delineate the layer at which the shear is active within 3-5 minutes from the receipt of the radar measured volume data by quickly computing elevation / vertical / radial / azimuthal shear etc. However, to arrive at a meaningful conclusion on the threshold values of shears that are conducive for wind shear induced turbulence and to make use of this information to alert the pilots, feed back from the pilots to build a detailed data base is absolutely inevitable. Monitoring of passage of sea breeze front may also be useful to issue wind shear warnings. The time tested Richardson number has also been verified for its ‘outlook predictability’ of the shear induced turbulence around the airport, though it can not pinpoint the exact location and the time at which turbulence is active. It is hoped that with precise, accurate and timely in-flight report about the wind shear experienced by the pilots and based on the experience gained in analyzing such information, it will be possible to issue probable ‘wind shear alert / warning’ in the near future.
Soil heat flux under irrigated, partially irrigated wheat and bare vertisol in relation to varying soil moisture and leaf area index at Pune
Authors: SAMUI R. P. , DHOTRE A. K. , JADHAV S. S. 
Published: January 2022

Soil heat flux as a function of moisture content in the drying cycles both under irrigated and partially irrigated wheat and in bare black vertisol was studied to relate temporal changes in soil heat fluxes to changes in leaf area index (LAI), soil water content and meteorological parameters. Moisture content dropped as low as 1 to 5 percent by weight at surface layer and 5 to 10 percent by weight at subsurface layers when irrigation was shut off under partially irrigated plot. The peak weekly mean global, net and reflected radiation during the crop growing season in this semi-arid region goes as high as 655, 361 and 179 Wm-2 respectively in the year 1996-97 and 700, 366 and 137 Wm-2 respectively during the year 1997-98. Soil temperature at 1430 hours IST ranged from 27 to 40°C at the surface (5.0 cm) layer under irrigated condition. It was 7 to 10° C and 2 to 3° C higher in the surface and subsurface layers respectively under partially irrigated wheat during the drying cycle. The upward soil heat flux ranged from -3.3 to -29.7 Wm-2 at 0730 hours IST, whereas downward heat flux at 1430 hours IST ranged between 8.4 to 33.9 Wm-2 under irrigated condition. Under partially irrigated condition it varied from -0.7 to -9.2 Wm-2 at 0730 hours IST and from 10.4 to 20.9 Wm-2 at 1430 hours IST; whereas it varied from -4.2 to -17.6 Wm-2 at 0730 hours IST and 6.7 to 24.7 Wm-2 at 1430 hours IST, under bare soil. The maximum mean heat fluxes into 5-20 cm soil depth under irrigated, partially irrigated and the bare soil were 10.2, 5.0 and 6.5 Wm-2 and 9.2, 7.1, and 6.7 Wm-2 respectively in the years 1996-97 and 1997-98. Soil temperature at 1430 hours IST both for irrigated wheat and bare vertisol and global radiation with soil temperature at 0730 hours IST under partially irrigated wheat were found to be the best predictors of soil heat flux. The relationships between soil heat flux and soil water content at different depth intervals along with LAI and other meteorological parameters could be used for estimation of soil heat flux, both for irrigated and partially irrigated wheat and bare soil.
Satellite analysis of tropical cyclones using NOAA-16 AMSU measurements over Indian region
Authors: SINGH DEVENDRA , BHATIA R. C. , SRIVASTAVA S. K. 
Published: January 2022

The first Advanced Microwave Sounding Unit (AMSU) was launched aboard NOAA-15 satellite on 13 May 1998. AMSU measurements are now also available from NOAA-16 and NOAA-17 satellites. The AMSU is well suited for the observation of tropical cyclones because the ice clouds that cover tropical cyclones do not significantly affect its measurements. In this paper the intensity of three tropical cyclones formed over Bay of Bengal and Arabian Sea in the month of October 1999, May and September 2001 were studied using AMSU measurements. The upper tropospheric warm core thermal anomalies over the tropical cyclone areas were computed from temperature profiles using the NOAA-15 and NOAA-16 AMSU-A measurements. It has been observed that the magnitude of the warm core temperature anomaly at about 250 hPa was an indicator of the intensity of tropical cyclones in all three cases. The order of the temperature anomaly was about 6oC in case of super tropical cyclone, 1999 while in other two cases the order of the temperature anomaly were of about 3oC for moderate tropical cyclones, 2001. Therefore, it may be stated that the AMSU data appeared to offer substantial opportunities for improvements in tropical cyclone analysis and forecasting.
Seasonal variation of 200 hPa upper tropospheric features over India in relation to performance of Indian southwest and northeast monsoons
Authors: RAJ Y. E. A. , SURESH R. , SANKARAN P. V. , AMUDHA B. 
Published: January 2022

The relation between 200 hPa upper tropospheric parameters such as temperature, zonal and meridional winds over India with the Indian southwest and northeast monsoons has been studied, based on monthly and seasonal upper air data of 14 well-distributed Indian radiosonde stations for the 36 year period 1963-98. It has been found that by and large, positive temperature/height anomalies, negative zonal wind anomalies and northerly position of the sub-tropical ridge during the preceding months/seasons are associated with good southwest/poor northeast monsoons and that complement of the above with poor southwest/good northeast monsoons. The profiles of the above relationship display a double peak in May and September/October. A multiple regression forecast scheme for seasonal forecasting of northeast monsoon rainfall, based on October data has been derived which when tested in an independent sample of 5 years yielded nearly 50% correct forecasts. The southwest monsoon rainfall of India and the northeast monsoon rainfall of Tamil Nadu/Southern parts of India have been shown to share a negative relationship, though the relationship is discordant rather than decisive, which gets defined better when years of deficient southwest monsoon rainfall get excluded. The feature of good Indian northeast monsoon getting preceded by colder upper tropospheric temperatures as shown in the study tie in well with the accepted mechanism of Asian winter monsoon getting intensified due to cold surges from the Siberian High.
Decadal and epochal variation of frequency and duration of monsoon disturbances and their secular relationship with rainfall over India
Authors: KUMAR J. RAJENDRA , THAPLIYAL V. , DASH S. K. 
Published: January 2022

Decadal and epochal variation of frequency and duration of monsoon disturbances like low pressure areas (lows), depressions and Cyclonic Storms (CS) over Indian region are studied by using 110 years (1890-1999) data. No linearly decreasing/increasing trend is observed during 110 years period in any of their frequencies. However, epochal linearly decreasing/increasing trends are noticed in decadal frequencies or duration of different monsoon disturbances. Decadal frequencies of depressions, CS and depressions are decreasing from 1970-79, till recently ended decade of 1990-99. During recent decade, less than half of the total number of depressions and CS are formed compared with 1970-79. On the other hand, total number of lows are increasing significantly from 1960-69 to recent decade, when more than double the number of lows of 1960-69 are formed.

Since Indian Summer Monsoon Rainfall (ISMR) also shows interdecadal variation of below normal and above normal phases, variation of frequencies of different monsoon disturbances and their total durations are also examined in similar time scale to understand their relationship with interdecadal variation of ISMR. Stability and secular nature of these relationships are also examined based on their decadal and 10-year moving Correlation Coefficients (CC) for the period 1890-1999. Relationship of decadal anomaly of their frequencies with interdecadal variation of ISMR shows that number of depressions and CS, are higher than the normal during the above normal ISMR decades and less during the below normal decades of ISMR. Reverse is true for the number of lows. The decadal and 10-years moving CC between ISMR and frequencies of different monsoon disturbances and total monsoon disturbance days clearly show epochal variation of their relationship in interdecadal time scale with ISMR. Hence present study shows that secular variation of CC not only exists between ISMR and its various regional and global parameters used in long range forecast of ISMR but also between ISMR and its main synoptic features e.g., monsoon disturbances.