Large scale features and assessment of spatial scale correspondence between TMPA and IMD rainfall datasets over Indian landmass

Abstract

Daily rainfall datasets of 10 years (1998-2007) of Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) version 6 and India Meteorological Department (IMD) gridded rain gauge have been compared over the Indian landmass, both in large and small spatial scales. On the larger spatial scale, the pattern correlation between the two datasets on daily scales during individual years of the study period is ranging from 0.4 to 0.7. The correlation improved significantly (∼0.9) when the study was confined to specific wet and dry spells each of about 5-8 days. Wavelet analysis of intraseasonal oscillations (ISO) of the southwest monsoon rainfall show the percentage contribution of the major two modes (30-50 days and 10-20 days), to be ranging respectively between ∼30-40% and 5-10% for the various years. Analysis of inter-annual variability shows the satellite data to be underestimating seasonal rainfall by ∼110 mm during southwest monsoon and overestimating by ∼150 mm during northeast monsoon season. At high spatio-temporal scales, viz., 1 • ×1 • grid, TMPA data do not correspond to ground truth. We have proposed here a new analysis procedure to assess the minimum spatial scale at which the two datasets are compatible with each other. This has been done by studying the contribution to total seasonal rainfall from different rainfall rate windows (at 1 mm intervals) on different spatial scales (at daily time scale). The compatibility spatial scale is seen to be beyond 5 • ×5 • average spatial scale over the Indian landmass. This will help to decide the usability of TMPA products, if averaged at appropriate spatial scales, for specific process studies, e.g., cloud scale, meso scale or synoptic scale.

Assessment of small-scale variability of rainfall and multi-satellite precipitation estimates using measurements from a dense rain gauge network in Southeast India

“…1, several evaluation studies exist in the literature focusing on the assessment of seasonal rainfall over India (Uma et al, 2013;Prakash et al, 2014;Sunilkumar et al, 2015), but none of them dealt with high-resolution (temporal) measurements. This aspect has been studied in detail in this section, in which the focus is primarily on the validation of high-resolution MPEs using a variety of metrics and statistical distributions and also on the diurnal cycle of rainfall.…”

“…It is, therefore, highly essential to perform validation independently at finer temporal scales over different climatic regions. As mentioned above, the evaluation of MPEs for monthly and seasonal monsoon precipitation was done to some extent over India (Rahman et al, 2009;Uma et al, 2013;Prakash et al, 2014;Sunilkumar et al, 2015). However, a detailed study on the validation of MPEs at shorter timescales (sub-daily and daily) does not exist due to the lack of suitable measurements.…”

Comparison of TMPA-3B42 Versions 6 and 7 Precipitation Products with Gauge-Based Data over India for the Southwest Monsoon Period

“…They noticed that TMPA picks up the west-to-east rainfall gradient along the west coast well, but the rainfall maxima over the Western Ghats are not captured adequately. More recently, Uma et al (2013) validated daily TMPA-3B42 V6 rainfall products with gridded IMD rain gauge-based data for the period of 1998-2007 and showed that TMPA picks up the major prominent large-scale features of the southwest or summer monsoon rainfall, like flood and drought and active and break spells, reasonably well. However, TMPA shows significant biases that vary across regions and seasons over India.…”

“…For the widest usage and applications of this precipitation product, a number of studies have been made in the last few years to validate this product at regional and seasonal scales (Sapiano and Arkin 2009;Villarini 2010;Scheel et al 2011;Karaseva et al 2012;Prakash et al 2012Prakash et al , 2013Prakash and Gairola 2014). However, there are relatively few studies available for the Indian land region (Rahman et al 2009;Nair et al 2009;Uma et al 2013;Prakash et al 2014b), which consists of varied topography and rainfall distributions. Rahman et al (2009) evaluated the TMPA-3B42 version 6 (V6) rainfall estimates with gridded rain gauge-based datasets from the India Meteorological Department (IMD) at daily scales and noticed that the TMPA product depicts the pattern and variability of rainfall reasonably well at synoptic scales.…”

Comprehensive evaluation of multisatellite precipitation estimates over India using gridded rainfall data

“…[] and Uma et al . [] have shown that satellite products are reasonably good on large spatial scales, but they differ very much from rain gauge data, both in the magnitude and variation, at smaller spatial scales. Nair et al .…”