صحّت سنجی داده های بارش ماهواره Gpm-Imerg در مقیاس‌های زمانی نیم‌ساعته و روزانه (مطالعه موردی: حوضه آبخیز گرگانرود)

ﺳﺎﺑﻘﻪ و ﻫﺪف: ﺟﻬﺖ ﺗﺨﻤﯿﻦ دﻗﯿﻖ ﺑﺎرش از روش ﻫﺎی ﻣﺨﺘﻠﻔﯽ از ﺟﻤﻠﻪ اﺳﺘﻔﺎده ﻣﺴﺘﻘﯿﻢ از داده ﻫﺎی اﯾﺴﺘﮕﺎه ﻫﺎی زﻣﯿﻨﯽ ﻫﻮاﺷﻨﺎﺳﯽ و ﻣﺸﺎﻫﺪات ﻣﺴﺘﻘﯿﻢ، ﺑﻪ ﮐﺎرﮔﯿﺮی داده ﻫﺎی ﻣﺎﻫﻮارﻫﺎی ﺳﻨﺠﺶ از دور و ﯾﺎ اﺳﺘﻔﺎده از روش ﻫﺎی دورن ﯾﺎﺑﯽ ﮐﻪ ﻣﺒﺘﻨﯽ ﺑﺮ روش ﻫﺎی زﻣﯿﻦ آﻣﺎر ﻫﺴﺘﻨﺪ، اﺳﺘﻔﺎده ﻣﯽ ﺷﻮد. اﺳﺘﻔﺎده از ﻓﻦ آوری ﻫﺎی ﺳﻨﺠﺶ از دور راداری در ﺗﺨﻤﯿﻦ دﻗﯿﻖ ﻣﻘﺪار ﺑﺎرش، اﻫﻤﯿﺖ ﺣﯿﺎﺗﯽ دارد. ﺑﻨﺎﺑﺮاﯾﻦ اﯾﻦ ﭘﮋوﻫﺶ ﺑﺎ ﻫﺪف ارزﯾﺎﺑﯽ دادهﻫﺎی ﺑﺎرش ﻣﺎﻫﻮاره gpm- imerg و ﻣﻘﺎﯾﺴﻪ آن ﺑﺎ داده ﻫﺎی اﯾﺴﺘﮕﺎه ﻫﺎی ﺑﺎران ﺳﻨﺠﯽ زﻣﯿﻨﯽ در اﺳﺘﺎن ﮔﻠﺴﺘﺎن- ﺣﻮﺿﻪ ﮔﺮﮔﺎن رود اﻧﺠﺎم ﺷﺪ. ﻣﻮاد و روش ﻫﺎ: ﭘﺲ از درﯾﺎﻓﺖ ﺳﺮی دادهﻫﺎی ﻣﺎﻫﻮاره ای gpm و ﭘﺮدازش اوﻟﯿﻪ آن ﻫﺎ، ﻣﻘﺎﯾﺴﻪ ﺗﻄﺒﯿﻘﯽ ﺑﯿﻦ دادهﻫﺎی ﻣﺎﻫﻮاره در ﻣﻘﯿﺎس زﻣﺎﻧﯽ ﻧﯿﻢﺳﺎﻋﺘﻪ و روزاﻧﻪ ﺑﺎ دادهﻫﺎی ﻣﺸﺎﻫﺪهای اﯾﺴﺘﮕﺎه ﺑﺎران ﺳﻨﺠﯽ زﻣﯿﻨﯽ (ﺛﺒﺎت و ﻣﻌﻤﻮﻟﯽ) اﻧﺠﺎم ﮔﺮﻓﺖ. ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ وﺿﻮح ﻣﮑﺎﻧﯽ (0/1 درﺟﻪ در 0/1 درﺟﻪ) و دﻗﺖ زﻣﺎﻧﯽ (اراﺋﻪ داده ﻫﺎی روزاﻧﻪ و 30 دﻗﯿﻘﻪ ای) داده ﻫﺎی imerg ﻣﺎﻫﻮاره gpm، ﺟﻬﺖ ﻣﻘﺎﯾﺴﻪ ﺗﻄﺒﯿﻘﯽ، ﺻﺤﺖ ﺳﻨﺠﯽ و ﺗﻌﯿﯿﻦ دﻗﺖ ﺗﺨﻤﯿﻦ ﺑﺎرش، از اﯾﺴﺘﮕﺎه ﻫﺎی ﺑﺎران ﺳﻨﺠﯽ ﺑﺎ دوره آﻣﺎری 2014/3/20- 2016/3/20 و 6 اﯾﺴﺘﮕﺎه ﺛﺒﺎت ﺑﺎ دوره آﻣﺎری 2016/9/21-2014/3/20 ﺣﻮﺿﻪ ﮔﺮﮔﺎﻧﺮود اﺳﺘﻔﺎده ﮔﺮدﯾﺪ. ﯾﺎﻓﺘﻪ ﻫﺎ: ﻧﺘﺎﯾﺞ ﻋﻤﻠﮑﺮد ﺑﺎرﻧﺪﮔﯽ ﻧﯿﻢ ﺳﺎﻋﺘﻪ imerg ﺑﺎ ﻣﻘﺎدﯾﺮ cc ﺑﺮاﺑﺮ ﺑﺎ 0/05-0/23 و csi ﺑﺮاﺑﺮ ﺑﺎ 0/20-0/52 ﻧﺴﺒﺘﺎً ﻗﺎﺑﻞ ﻗﺒﻮل ارزﯾﺎﺑﯽ ﺷﺪ. اﻋﺘﺒﺎرﺳﻨﺠﯽ داده ﻫﺎی ﺑﺎرش ﻣﺎﻫﻮاره gpm ﺑﺎ اﺳﺘﻔﺎده از ﺷﺎﺧﺺ ﻫﺎی آﻣﺎری mae، rmse و mbe ﻧﯿﺰ از دﻗﺖ ﻧﺴﺒﺘﺎً ﻗﺎﺑﻞ ﻗﺒﻮﻟﯽ ﺑﺮﺧﻮردار ﺑﻮده اﺳﺖ. ﺑﺮ اﺳﺎس اﻋﻤﺎل ﺷﺎﺧﺺ ﻫﺎی ﻣﺮﺑﻮط ﺑﻪ ﻣﻘﺎﯾﺴﻪ روزاﻧﻪ اﯾﺴﺘﮕﺎه ﻫﺎی ﺑﺎران ﺳﻨﺠﯽ ﺑﺎ داده ﻫﺎی ﻣﺎﻫﻮاره gpm، ﺷﺎﺧﺺ rbias ﺑﺎ ﻣﻘﺪار 0/74 ﺑﺎﻻﺗﺮﯾﻦ ﻣﯿﺰان ﻣﻄﺎﺑﻘﺖ داده ﻫﺎی gpm ﺑﺎ داده ﻫﺎی ﻣﺸﺎﻫﺪه ای را داﺷﺖ و ﮐﻢ ﺗﺮﯾﻦ ﻣﯿﺰان ﻣﻄﺎﺑﻘﺖ ﺑﺎ ﻣﻘﺪار 2/27 ﻣﺮﺑﻮط ﺑﻪ اﯾﺴﺘﮕﺎه ﻧﻮده ﻣﯽ ﺑﺎﺷﺪ. ﺷﺎﺧﺺ pod ﻧﯿﺰ ﻧﺸﺎن داد ﮐﻪ اﯾﺴﺘﮕﺎه ﻫﺎی ﻧﻮده و ﺣﻖ اﻟﺨﻮاﺟﻪ ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﺎ ﻣﻘﺎدﯾﺮ 0/5 و 0/25 ﺑﯿﺶ ﺗﺮﯾﻦ و ﮐﻢ ﺗﺮﯾﻦ ﻣﻄﺎﺑﻘﺖ را ﺑﺎ اﯾﺴﺘﮕﺎه ﻫﺎی زﻣﯿﻨﯽ داﺷﺘﻪ اﺳﺖ. ﺑﺮاﺳﺎس ﻣﻘﺎدﯾﺮ ﺷﺎﺧﺺ ﻣﻄﺎﺑﻘﺖ far ﻣﻼﺣﻈﻪ ﺷﺪ ﮐﻪ ﮐﻢ ﺗﺮﯾﻦ ﻣﻘﺪار far در اﯾﺴﺘﮕﺎهﻫﺎی ﺑﺎغ ﺳﺎﻟﯿﺎن و زرﯾﻨﮕﻞ 0/64 و ﺑﯿﺶ ﺗﺮﯾﻦ ﻣﻘﺪار 0/80 در اﯾﺴﺘﮕﺎه ﺷﯿﺮآﺑﺎد ﻣﯽ ﺑﺎﺷﺪ. ﺑﻮده اﺳﺖ. ﻧﺘﯿﺠﻪ ﮔﯿﺮی: اﻋﺘﺒﺎرﺳﻨﺠﯽ داده ﻫﺎی ﺑﺎرش ﻣﺎﻫﻮاره gpm ﺑﺎ اﺳﺘﻔﺎده از ﻣﻌﯿﺎرﻫﺎی آﻣﺎری rmse ،mae و mbe ﻧﯿﺰ ﻧﺸﺎن داد ﮐﻪ از دﻗﺖ ﻗﺎﺑﻞ ﻗﺒﻮﻟﯽ ﺑﺮﺧﻮردار اﺳﺖ. ﻣﻘﺎدﯾﺮ pod ﻧﯿﺰ ﻋﻤﻠﮑﺮد ﻗﺎﺑﻞ ﻗﺒﻮل داده ﻫﺎی اﯾﻦ ﻣﺎﻫﻮاره را ﻧﺸﺎن داده اﺳﺖ. ﻧﺘﺎﯾﺞ اﯾﻦ ﭘﮋوﻫﺶ ﻧﯿﺰ ﻧﺸﺎن داد ﮐﻪ ﻣﻄﺎﺑﻘﺖ ﻧﺴﺒﯽ و ﺧﻮﺑﯽ ﺑﯿﻦ داده ﻫﺎی اﯾﺴﺘﮕﺎﻫﺎی زﻣﯿﻨﯽ و داده ﻫﺎی ﻣﺎﻫﻮاره ای gpm وﺟﻮد داﺷﺘﻪ اﺳﺖ.

Accuracy assessment of GPM-IMERG satellite precipitation data on half-hourly and daily time scales (Case study: Gorganroud Basin)

Background and Objectives: Precipitation is one of the most important factors affecting water and energy balance in the world and important meteorological variables. To accurately estimate precipitation, various methods are used, including the direct use of meteorological ground station data and direct observations, the use of remote sensing satellite data, or the use of interpolation methods based on geostatistical methods. Therefore, developing innovative approaches for accurate estimation of precipitation in areas with inadequate or inadequate data is critical. The use of radar remote sensing technologies in the accurate estimation of precipitation is crucial as the most important factor affecting water and energy balance in areas with unsuitable and inadequate data. Therefore, this research was conducted to evaluate GPMIMERG satellite precipitation data and compare it with the data of observatory stations in the Golestan provinceGorganroud basin.Materials and Methods: To do this research, after obtaining the GPM satellite data and processing it, we performed a comparison between halfhourly daily satellite data set with the groundbased (stability and normal) observational data. Concerning the spatial (0.1*0.1) and temporal (daily and halfhourly) resolutions of GPMIMERG satellite data, we employed enough and valid groundbased rainfall records dated 20/03/201420/03/2016 (for daily series) and 20/03/201421/09/2016 (for halfhourly series). To assess the accuracy of GPM data in rainfall estimation, some statistical indicators such as FAR , CSI , POD , RBias and some other validation indicators were used.Results: The results showed that the halfhour rainfall IMERG records with CC values equal to 0.050.23 and CSI equal to 0.200.52 were relatively acceptable. Validation of GPM satellite rainfall data using MAE, RMSE, and MBE statistical indicators has also been relatively acceptable. Based on the validation analysis of daily records, the RBias index showed the highest level of accordance of GPM data with observational data at 0.74 , and the lowest level corresponding to 2.27, that belongs to Nodeh station. The POD index also showed that Nodeh and HagholKhajeh stations had the highest and lowest correspondence with ground stations with the values of 0.5 and 0.25, respectively. The values of the CSI index in all stations were calculated to be between 0.13 and 0.22, which were related to Zarrin Gol and Shirabad stations, respectively. Based on the values of the FAR index, it was observed that the lowest value of FAR in Bagh Salian and Zarringol stations was 0.64 and the highest value was 0.80 in Shirabad station. Therefore, to improve the data obtained from the IMERG algorithm, especially in arid regions with the extensive spatial distribution and temporal changes in precipitation, satellite precipitation products should be calibrated to improve their accuracy in measuring daily precipitation.Conclusion: In this study, the calculation of statistical and matching indicators was performed for the first time to compare halfhour data of the GPM satellite with observational data. It was found that the IMERG algorithm of the GPM satellite is relatively consistent with the recorded values of ground stations daily, as well. Given the FAR values at all stations, it can be said that there is a relative correspondence between satellite data and observed data from ground stations. POD values also showed acceptable performance of this satellite’s data. The results of this study also showed that there was a relative correlation between the data of ground stations and GPM satellite data. Therefore, considering the nonevaluation of precipitation data of the GPM satellite system with data of ground stations in many regions of Iran, including the study area of Gorganroud, the results of this study can be very useful for innovation and increasing the efficiency in water resources management.