MT-MADRAS brightness temperature analysis for terrain characterization and land surface microwave emissivity estimation

This article reports the potential of the ‘MADRAS’ payload on-board the Megha-Tropiques satellite for land surface studies. The analysis has been divided into two parts as application of MADRAS data for studying the land surface properties and estimation of microwave emissivity directly from MADRAS brightness temperature (TB) data by applying an in-house developed Microwave Radiative Transfer Computation Code. The derived emissivity is further used to characterize the microwave emissivity of different land surface classes. The polarization difference (PD) parameters, the difference between horizontal (H-) and vertical (V-) polarization of TBs at 18 and 36 GHz clearly discern surface features of different surface classes such as deserts, arid/semi-arid an d vegetated regions. Land surface microwave emissivity for MADRAS channels is derived on a global basis. These are inter-compared with the emissivity derived from the operational TRMM Microwave Imager and are in reasonably good agreement. The analysis based on emissivity shows spectral variation for different surface classes

A detailed study of land surface microwave emissivity over the Indian subcontinent

Microwave emissivities of land surfaces on global basis have been derived using Special Sensor Microwave/Imager brightness temperature data. These derived emissivities are compared with other reported emissivity values to demonstrate the accuracy of the retrievals. Following these results, detailed analyses on the microwave emissivities of the Indian subcontinent are carried out using the monthly mean emissivity estimate for two years. The Indian subcontinent has a wide variety of geographic and biospheric classes with distinctly different emissivity characteristics. The spectral and monthly variations of microwave emissivity for different tropical land surface classes are examined. This study is significant for microwave radiance assimilation in weather forecast models and also for the utilization of the data from passive microwave sensors onboard the Indo-French satellite “Megha-Tropiques,” which is dedicated to tropical atmospheric studies

Microwave radiometer observations of interannual water vapor variability and vertical structure over a tropical station

The intraseasonal and interannual characteristics and the vertical distribution of atmospheric water vapor from the tropical coastal station Thiruvananthapuram (TVM) located in the southwestern region of the Indian Peninsula are examined from continuous multiyear, multifrequency microwave radiometer profiler (MRP) measurements. The accuracy of MRP for precipitable water vapor (PWV) estimation, particularly during a prolonged monsoon period, has been demonstrated by comparing with the PWV derived from collocated GPS measurements based on regression model between PWV and GPS wet delay component which has been developed for TVM station. Large diurnal and intraseasonal variations of PWV are observed during winter and premonsoon seasons. There is large interannual PWV variability during premonsoon, owing to frequent local convection and summer thunderstorms. During monsoon period, low interannual PWV variability is attributed to the persistent wind from the ocean which brings moisture to this coastal station. However, significant interannual humidity variability is seen at 2 to 6 km altitude, which is linked to the monsoon strength over the station. Prior to monsoon onset over the station, the specific humidity increases up to 5–10 g/kg in the altitude region above 5 km and remains consistently so throughout the active spells

Flood extent analysis over the major river basins in the Indian subcontinent using satellite microwave radiometric data

Every year South Asia suffers from widespread floods along its major river basins, especially during the southwest monsoon season calling for planning, mitigation, and hazard management strategies. This study demonstrates the application of land surface microwave emissivity data in identifying and quantifying flooded areas. It employs an indigenously developed scheme based on microwave radiative transfer to retrieve emissivities at 19 GHz from satellite microwave radiometers and to estimate emissivity polarization index ($EPI$) from it. By assigning thresholds to the $EPI$ for delineating inundated areas, this study examines the inter-annual variability of floods over the Indo-Gangetic plains for the period 2007–2010 and the cataclysmic flood of 2010 in Pakistan

Vitamin B-12 Intake and Status in Early Pregnancy among Urban South Indian Women

AIM: To evaluate the vitamin B(12) status of South Indian women in early pregnancy and its relationship with sociodemographic, anthropometry and dietary intake. METHODS: Cross-sectional study among 366 pregnant urban South Indian women ≤14 weeks of gestation with outcome variables defined as low vitamin B(12) blood concentration (<150 pmol/L) and impaired vitamin B(12) status [low vitamin B(12) plus elevated methylmalonic acid (MMA) >0.26 μmol/L)]. RESULTS: Low plasma vitamin B(12) concentration was observed in 51.1% of the women, while 42.4% had impaired B(12) status. Elevated MMA, elevated homocysteine ( >10 μmol/L) and low erythrocyte folate (<283 nmol/L) was observed among 75.8%, 43.3% and 22.2% of women, respectively. The median (25(th), 75(th) percentile) dietary intake of vitamin B(12) was 1.25 (0.86, 1.96) μg/day. Lower maternal body weight was associated with higher vitamin B(12) concentration [prevalence ratios (PR) (95% CI) 0.57 (0.39, 0.84)). The predictors of impaired vitamin B(12) status were non-use of yoghurt [PR (95%CI) 1.63 (1.03, 2.58)], non-use of fish [PR (95% CI) 1.32 (1.01, 1.71)] and primiparity [PR (95% CI) 1.41 (1.05, 1.90)]. CONCLUSION: A high prevalence of vitamin B(12) deficiency in early pregnancy among urban South Indian women was related to primiparity and to a low consumption of yoghurt and fish