Use of satellite data for radiative energy budget study of Indian summer monsoon

In this paper satellite-derived radiative energy budget such as shortwave radiative heating, longwave radiative heating and net radiation balance have been studied for the post-onset phase of summer monsoon 1979. Since clouds play an important role in determining diabatic heating field as well as being a reflection of status of the monsoon itself, the day to day evolution of clouds from TIROS-N satellite has been made. Satellite-derived radiative heating rates from surface to 100 hPa were computed for each 100 hPa thickness layer. These heating rates were then compared with the observed latitudinal distribution of total radiative heating rates over the domain of the study. From the results of our study it was found that the characteristic features such as net radiative heating rates of the order of 0.2°C/day at upper tropospheric layer (100-200 hPa) and cooling throughout the lower tropospheric layers with relatively less cooling between 500-700 hPa layer observed in a case of satellite-derived radiative energy budget agree well with the characteristic features of observational radiative energy budget over the domain of the study. Therefore, it is suggested that radiative energy budget derived from satellite observations can be used with great potential and confidence for the evolution of the complete life cycle of the monsoon over the Indian region for different years

Satellite-observed upwelled region and prime eddy off Somali coast during Monex-79

An upwelled region as seen through satellite imagery off the Somali coast is compared with sea surface temperature during summer Monex-79. The relationship between satellite-derived low-level cloud drift winds and the sea-surface temperature is studied. Cloudiness associated with a prime eddy off the Somali coast is also studied. It is observed that the upwelled region has a unique crescent shape and reflects the sea-surface temperature that is driven by low-level strong winds. The prime eddy, as observed through a satellite imagery, shows that low cloud convection tends to be greater over the warm waters of the prime eddy, and the upwelled cold water tends to encircle the eddy leading to the identification of its outer boundary

Utility of DMSP-SSM/I for integrated water vapour over the Indian seas

Recent algorithms for Special Sensor Microwave/Imager (DMSP-SSM/I) satellite data are used for estimating integrated water vapour over the Indian seas. Integrated water vapour obtained from these algorithms is compared with that derived from radiosonde observations at Minicoy and Port Blair islands. Algorithm-3 of Schlussel and Emery (1990) performed best. On the basis of this algorithm, distribution of integrated water vapour is determined during the monsoon depression (22nd-27th July, 1992) that formed over the Bay of Bengal

Satellite observed wind forcing over the southwest equatorial Indian ocean during Indian summermonsoon

In this paper, satellite-observed wind forcing in the form of strong surge of cold air through Mozambique channel and along east African coast, under the influence of eastward propagating baroclinic wave disturbances over southwest Indian ocean has been studied during various summer monsoon seasons. Further, its impact on the intensification of monsoon systems over the Arabian sea through the excitation of low-level jet and associated cross-equatorial flow has been illustrated. For this purpose, satellite-observed cloud imagery, obtained from TIROS-N, NOAA, DMSP, GOES and INSAT satellites during 1979 and 1988-95,have been utilized for finding latitudinal positions of the cold fronts across south African-Malgassy region (i.e. 30°S, I -40°E), GOES(IO) and INSAT derived low level cloud drift winds in the domain 2.5°S to 2.5°N and 40°50°E have been used to observe the triggering of low level jet and associated cross equatorial flow. Daily rainfall of ten stations viz. Tiruvananthapuram, Alleppy, Cochin, Kozikhode, Mangalore, Karwar, Goa, Ratnagiri, Bombay and Dahanu have been used for finding the modulation of the rainfall activity along the west coast of India. From the results of the study it is inferred that there is an abrupt increase in the strength of low-level wind flow along east African coast 2 to 3 days after the first appearence of northward propagating cold front across south African-Malgassy region. This is followed by intensification of the rainbearing monsoon systems (e.g. ITCZ, lows, off shore troughs etc.) over the Arabian sea giving increase in rainfall activity along the west coast of India. Therefore it is suggested that above association between northward-propagating cold front across south African-Malgassy region and excitation of low-level cross-equatorial flow can be linked to forecast increase in rainfall activity alone the west coast of India 5-7 days in advance

Response of the Bay of Bengal to Gopalpur and Paradip super cyclones during 15-31 October 1999

Response of the Bay of Bengal to two tropical cyclones, i.e. Gopalpur and Paradip super cyclones, during 15-31 October 1999, is studied using a stationary mooring buoy for marine meteorological observations. The National Institute of Ocean Technology (NIOT, Chennai) has deployed this buoy at 13°N, 87°E, by fixing various meteorological instruments and sensors to acquire sea surface temperature (SST), air temperature (Ta), wind speed (Ws), wind direction (Wd) and ocean currents (Cs) using remote sensing technique through INSAT-1D satellite at an interval of 3 h. The results of the analysis of the above parameters have shown clearly a response (SST difference between before and after formation) of about 0.7°C for the Gopalpur cyclone and 0.9°C for the Paradip cyclone. Ta has shown rapid variations following the rapid movement of cloud decks across the buoy during the cyclone period. The observed changes in the wind speed and direction are in concurrence with analysed mean sea level pressure oscillations. Finally, this study recommends more buoy-based marine meteorological observations over this region and the neighbouring areas, where the tropical cyclones generally occur and subsequently hit the Coromandal coast

Investigation of features of May, 2001 tropical cyclone over the Arabian Sea through IRS-P4 and other satellite data

In this paper, utility of satellite derived atmospheric motion vectors and geophysical parameters is brought out to discern appropriate signals for improving short-range forecasts in respect of development/dissipation of tropical cyclones over the Indian region. Results of a particular case study of May, 2001 cyclone, which formed in the Arabian Sea are reported. Analysis of wind field with input of modified cloud motion vectors and water vapour wind vectors is performed utilizing Optimum Interpolation (OI) technique at 850 and 200 hPa for finding dynamical changes such as vorticity, convergence and divergence for the complete life period of this cyclone. Simultaneously, variations in geophysical parameters obtained from IRS-P4 and TRMM satellites in ascending and descending nodes are compared with dynamical variations for discerning some positive signals to improve short range forecasts over the Indian region. The enhancement of cyclonic vorticity at 200 hPa over larger area surrounding center of cyclone was observed from 26 to 28 May 2001 which gave a positive signal for dissipation of storm

Proper depiction of monsoon depression through IRS-P4 MSMR

In this paper, daily variations of satellite-derived geophysical parameters such as integrated water vapour (IWV), cloud liquid water content (CLW), sea surface temperature (SST) and sea surface wind speed (SSW) have been studied for a case of monsoon depression that formed over the Bay of Bengal during 19th-24th August 2000. For this purpose, IRS P4 MSMR satellite data have been utilized over the domain equator - 25°N and 40°-100°E. An integrated approach of satellite data obtained from IRS-P4, METEOSAT-5 and INSAT was made for getting a signal for the development of monsoon depression over the Indian region. Variations in deep convective activity obtained through visible, infrared and OLR data at 06 UTC was thoroughly analyzed for the complete life cycle of monsoon depression. Geophysical parameters obtained through IRS-P4 satellite data were compared with vorticity, convergence and divergence at 850 and 200 hPa levels generated through cloud motion vectors (CMVs) and water vapour wind vectors (WVWVs) obtained from METEOSAT-5 satellite. This comparison was made for finding proper consistency of geophysical parameters with dynamical aspects of major convective activity of the depression. From the results of this study it is revealed that there was strengthening of sea surface winds to the south of low-pressure area prior to the formation of depression. This indicated the possibility of increase in cyclonic vorticity in the lower troposphere. Hence, wind field at 850 hPa with satellite input of CMVs in objective analysis of wind field using optimum interpolation (OI) scheme was computed. Maximum cyclonic vorticity field at 850 hPa was obtained in the region of depression just one day before its formation. Similarly, with the same procedure maximum anticyclonic vorticity was observed at 200 hPa with WVWVs input. Consistent convergence and divergence at 850 and 200 hPa was noticed with respect to these vorticities. In association with these developments, we could get lowest values of OLR (120W/m 2) associated with major convective activity that was consistent with the maximum values of integrated water vapour (6-8 gm/cm 2) and cloud liquid water content (50-60 mg/cm 2) persisting particularly in the southwest sector of the monsoon depression

Mesenchymal-epithelial signalling in tumour microenvironment: role of high-mobility group Box 1.

Glucose deprivation, hypoxia and acidosis are characteristic features of the central core of most solid tumours. Myofibroblasts are stromal cells present in many such solid tumours, including those of the colon, and are known to be involved in all stages of tumour progression. HMGB1 is a nuclear protein with an important role in nucleosome stabilisation and gene transcription; it is also released from immune cells and is involved in the inflammatory process. We report that the microenvironmental condition of glucose deprivation is responsible for the active release of HMGB1 from various types of cancer cell lines (HT-29, MCF-7 and A549) under normoxic conditions. Recombinant HMGB1 (10 ng/ml) triggered proliferation in myofibroblast cells via activation of PI3K and MEK1/2. Conditioned medium collected from glucose-deprived HT-29 colon cancer cells stimulated the migration and invasion of colonic myofibroblasts, and these processes were significantly inhibited by immunoneutralising antibodies to HMGB1, RAGE and TLR4, together with specific inhibitors of PI3K and MEK1/2. Our data suggest that HMGB1 released from cancer cells under glucose deprivation is involved in stimulating colonic myofibroblast migration and invasion and that this occurs through the activation of RAGE and TLR4, resulting in the activation of the MAPK and PI3K signalling pathways. Thus, HMGB1 might be released by cancer cells in areas of low glucose in solid tumours with the resulting activation of myofibroblasts and is a potential therapeutic target to inhibit solid tumour growth

Microfold (M) cells: important immunosurveillance posts in the intestinal epithelium

The transcytosis of antigens across the gut epithelium by microfold cells (M cells) is important for the induction of efficient immune responses to some mucosal antigens in Peyer’s patches. Recently, substantial progress has been made in our understanding of the factors that influence the development and function of M cells. This review highlights these important advances, with particular emphasis on: the host genes which control the functional maturation of M cells; how this knowledge has led to the rapid advance in our understanding of M-cell biology in the steady-state and during aging; molecules expressed on M cells which appear to be used as “immunosurveillance” receptors to sample pathogenic microorganisms in the gut; how certain pathogens appear to exploit M cells to infect the host; and finally how this knowledge has been used to specifically target antigens to M cells to attempt to improve the efficacy of mucosal vaccines