Gridded data as a source of missing data replacement in station records

Abstract

The quality of available station data over western Himalayan region (WHR) of India is poor due to missing values, and hence quantifying climate change information at the station level is more challenging. The present study investigated the extent to which the available two different resolutions gridded rainfall data from the India Meteorological Department (IMD) namely, IMD-0.25 ∘ × 0.25 ∘ (IMD.25) and IMD-1 ∘ × 1 ∘ (IMD1) and global observational gridded data from the Climate Research Unit (CRU-0.5 ∘ × 0.5 ∘ ) of UK can be used as a substitute to replace the missing values in IMD station data. Long-term time series produced at each station location showed that IMD.25 data was much closer to observation both in magnitude and patterns compared to CRU and IMD1. The seasonal and annual scale performance of these gridded data has been evaluated through different agreement and error indices. The agreement indices showed higher values in case of IMD.25 data while IMD1 and CRU indicated poor results. Similarly, the estimated errors are minimum in IMD.25 and maximum in CRU data. Finally, an overall agreement index (OAI) was developed by the combined influence of all the agreement indices. The results of OAI for each station revealed that in more than 77% of cases, the performance of IMD.25 gridded data to reproduce station level rainfall is superior as compared to IMD1 (<63%) and CRU (<46%) data. Therefore, it is concluded that the IMD.25 gridded data may be reliably used as a substitute data source in place of missing rain-gauge data over the WHR.