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Browsing by Author "Singh, Prasamsa"

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    Altitudinal variability of monsoon precipitation over mountainous region
    (2004) Singh, Prasamsa; Prajapati, Shiva Bhakta
    The study conducted some investigations to know the relationship between topographic effects on rainfall distribution with regards to the topographic elevation over Mountainous region. Comparison of relationship between topographic effects on rainfall distribution with relation to the topographic elevation using ground based data of one hundred and ninety one rain gauge stations within domain of latitude 27.30' to 29.40' and longitude 80.00' to 84.00' of period June - August (1998- 2000) and Tropical Rainfall Measuring Mission/ Precipitation Radar (TRMM/ PR) within domain latitude 26.00' to 32.00' and longitude 75.00' to 80. 00' of the same duration are characterized relatively well. Digital elevation map (DEM) with spatial resolution 30 sec (Gtopo30) is used for spatial topographic study. Much attention was focused on "effective height for precipitation" i.e. topographic height where amount of rainfall is high. It was found through investigation that the rainfall decreases beyond 1800m using ground based data and rainfall decreases beyond 2100m using TRMM data.
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    Diurnal variation in summer monsoon precipitation during active and break periods over central India and southern Himalayan foothills
    (2010) Singh, Prasamsa; Nakamura, Kenji
    The diurnal variations of summer precipitation over central India and the southern Himalayan foothills are investigated using Tropical Rainfall Measuring Mission (TRMM) data for July–August from 1998 to 2007. The TRMM precipitation radar (PR) and Lightning Imaging Sensor (LIS) data are used to understand characteristics of precipitation. Daily data from TRMM/3B42 are used to determine active and break periods in central India on the basis of rainfall characteristics. Diurnal variation in rain rate, frequency of rain, conditional rain rate, storm height, and occurrence of convective rain is analyzed using TRMM/PR data (0.1° × 0.1° resolution). Diurnal variation in total lightning flashes is analyzed using TRMM/LIS data. The precipitation over central India during wet periods is characterized by a large amount of rainfall with a high frequency of rain and a secondary morning peak. The precipitation in dry periods is characterized by a strong diurnal variation with convective rainfall and enhanced electrical activity over central India. Characteristics of wet and dry periods over central India are generally supported over the southern Himalayan foothills. Copyright American Geophysical Union.
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    Diurnal variation in summer precipitation over the central Tibetan Plateau
    (2009) Nakamura, Kenji; Singh, Prasamsa
    The diurnal cycle of rainfall over the central Tibetan Plateau was investigated by examining data acquired by the Tropical Rainfall Measuring Mission Precipitation Radar during the summer monsoon season (June–August) from 1998–2007. High-spatial-resolution data ( 5 km 5 km) were used to identify the role of complex topographic features of the plateau. Diurnal variations in rain rate, frequency of rain, conditional rain rate, and storm-height were analyzed on a monthly basis to determine the characteristics of precipitation. The results are interpreted as precipitation characteristics in a semiarid region with weak prevailing winds. Distinct diurnal variation was seen over hilly regions, valleys, and lakes. Precipitation activity over the hilly region is generally strongest during the late afternoon. But in contrast, valleys and lakes show dominant late-evening peaks, and a secondary morning rainfall peak is distinctly evident over large lakes. However, the time of peak rain rate is delayed with increasing lake size. The shift in rain peak location toward lakes and valleys also appeared clearly. Copyright American Geophysical Union.
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    Diurnal variation of precipitation over Himalayan region
    (2004) Singh, Prasamsa; Furuzawa, F. A.; Nakamura, Kenji
    The diurnal cycle of precipitation is one of the strongest components of variablility of precipitation. The study was focused on diurnal variation of precipitation normal to the Himalayan range using the Tropical Rain Measuring Mission (TRMM) Precipitation Radar (PR), instantaneous data over the period 1998-2002. Gtopo30 (Digital elevation map (DEM) with spatial resolution 30 was used for study topographic height. During June, July and August late night/morning rainfall is dominated over the slope and foothill of mountains, while afternoon/evening rainfall dominated over Tibetan Plateau and Deccan Plateau. Foothill of the mountain and Deccan Plateau is characterized by convective rainfall where as Tibetan plateau and slope of the mountain is characterized by stratiform rainfall. It is also noticed that rainfall shifts southward during morning period.
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    Spatiotemporal variation of rainfall over the central Himalayan region revealed by TRMM Precipitation Radar
    (2012) Shrestha, Dibas; Singh, Prasamsa; Nakamura, Kenji
    The rainfall-elevation relationship in the central Himalayan region (CHR) for premonsoon and monsoon seasons is analyzed utilizing the 11-year (1998–2008) high-spatialresolution TRMM PR 2A25 near-surface rainfall data. The results indicate a strong relationship between rainfall and elevation during both seasons. The investigation reveals a relatively large amount of rainfall over higher elevations during pre-monsoon season. Interestingly, two significant rainfall peaks appear over the southern slope of the Himalayas during summer monsoon season. The first primary peak appears along the Sub-Himalayas ( 500–700 m above MSL), while the second appears along the Lesser Himalayas ( 2,000–2,200 m above MSL). The former rainfall peak is attributed to fewer heavy rainfall events, and the latter to frequent, weak, but persistent rainfall. It is suggested that the atmosphere is insufficiently moist to trigger convections during the pre-monsoon season, and sufficiently moist during summer monsoon season. The convections over the Sub-Himalayas may moisten the middle layer, and the water vapor in the atmosphere condenses because of the forced lifting along the slope, forming the second rainfall band. The total rain amount is primarily determined by the frequency of rain. The rainconditioned rain rate along the slope monotonically decreases with elevation. This shows that the precipitation occurs because of forced lifting. In addition, our results show that seasonal variation of rainfall is rather similar to the variation of rainfall characteristics observed during active and break periods. Copyright American Geophysical Union.