نوع مقاله : مقاله پژوهشی
موضوعات
عنوان مقاله English
نویسندگان English
Aim: This study investigates the accuracy and reliability of GPCC and CRU data for conducting various hydroclimatic studies in Iraq.
Material & Method: The data used include monthly precipitation data from the GPCC database with a spatial resolution of 0.5° and 0.25° geographical latitude and longitude, and monthly precipitation, minimum and maximum temperature data from the CRU database with a spatial resolution of 0.5° geographical latitude and longitude over the period 1990–2020. R, R2, EF, BIAS, RMSE, and Slope statistics were used to evaluate the accuracy of the data.
Finding: According to the validation results, GPCC and CRU exhibit satisfactory accuracy in estimating precipitation minimum and maximum temperatures in Iraq. GPCC shows a high correlation coefficient (0.71-0.87) in estimating precipitation in Iraq's eastern and northern provinces. The Slope statistic ranges between 0.80 and 1.2, and the NRMSE is less than 3 in most stations. CRU demonstrates a high correlation coefficient (R≈0.81), EF>0.5, NRMSE<2, and Bias between -2 and 6 mm in estimating precipitation in the eastern and northern parts of the country. Furthermore, CRU exhibits high accuracy in estimating minimum and maximum temperature in Iraq; as such, the CRU data and observed data at stations exhibit strong agreement, with R>0.96, R2>0.95, EF>0.95, Slope>0.95, and NRMSE around less than 1.5 in most regions.
Conclusion: Based on the validation results, GPCC and CRU have suitable accuracy in estimating rainfall minimum and maximum temperatures in Iraq. Therefore, GPCC and CRU data can be introduced as reliable sources for analyzing precipitation and temperature patterns and in areas lacking data in Iraq.
Innovation: Both data sources provide the possibility of analyzing precipitation and temperature patterns, as well as important decision-making steps related to water management and adaptation to climate change.
کلیدواژهها English
1. Introduction
In research related to atmospheric sciences and hydrology, one of the fundamental challenges for researchers is the lack of access to accurate and long-term data. The inadequate distribution of synoptic and rainfall stations or the occurrence of various errors in measuring variables can lead to statistical defects and a lack of access to accurate data. Therefore, using information recorded by databases can effectively complement filling these information gaps. Accurate and reliable rainfall and temperature data are essential for water resource management, agricultural planning, and climatic research, especially in countries like Iraq, which face significant uncertainty and water scarcity. However, collecting ground measurements in Iraq can be challenging due to limited infrastructure, political instability, and environmental characteristics.
2. Materials and methods
The study area is Iraq in Western Asia. The data used in this study include rainfall data from the GPCC (Global Precipitation Climatology Centre) with a spatial resolution of 0.25° and 0.5° and rainfall, minimum, and maximum temperature data from the CRU (Climatic Research Unit) with a spatial resolution of 0.5°. Additionally, monthly rainfall and minimum and maximum temperature data from 17 synoptic stations in Iraq over 31 years (1990–2020) were used. These data were obtained for 172 points across Iraq. The rainfall and temperature values from the two databases were extracted and compared to the observed data. Five statistics (R, R2, EF, BIAS, RMSE, and Slope) were used to evaluate the accuracy of the gridded data against observed data. In the final step, using these five statistical tests and programming in MATLAB, the observed data matrix was compared and evaluated with the gridded data matrix, and the error of each database in estimating rainfall and temperature was identified and presented as a map.
3. Discussion and results
The lack of accurate and long-term data is one of the main challenges for researchers in climate and water resource studies. In many arid and mountainous regions, synoptic and rainfall stations are not distributed at suitable intervals. Therefore, data from existing databases worldwide can be a suitable complement to address these gaps. In this study, monthly rainfall data from the GPCC and CRU datasets and monthly minimum and maximum temperature data were evaluated against observed data from 17 stations in Iraq over the period 1990–2020. The findings of this study show that GPCC and CRU data have moderate to high accuracy in simulating rainfall in different regions of Iraq. The highest accuracy of these two datasets was estimated in the eastern, northern, and southeastern regions of Iraq. Regarding minimum and maximum temperature data, the CRU dataset provides reliable data for use in different regions of Iraq. The evaluation of these datasets in Iraq can confirm the results of other studies on the suitability of GPCC and CRU in Iraq and other world regions. The validation results of GPCC rainfall data show that these data have acceptable accuracy and efficiency in estimating rainfall in most parts of the country, especially in the eastern and northern regions of Iraq. Additionally, the spatial accuracy of these data is satisfactory in most areas, and they can represent the rainfall patterns in the region well. The validation of CRU rainfall data shows that this dataset also has high accuracy and a desirable ability to estimate rainfall, especially in northern and eastern Iraq. The spatial distribution of these data in Iraq indicates their accuracy and compatibility with observed data at stations. In terms of comparing the evaluation statistics of the two rainfall datasets, GPCC and CRU do not show any significant superiority over each other. The minimum and maximum temperatures of the CRU dataset also show suitable accuracy in estimating and representing the spatial pattern of these variables across Iraq.
4. Conclusion
Based on the validation results, GPCC and CRU have suitable accuracy in estimating rainfall and minimum and maximum temperatures in Iraq. GPCC has high correlation coefficients (0.71-0.87) in estimating rainfall in the eastern and northern provinces of Iraq. The Slope statistic is between 0.8 and 1.2, and the NRMSE is less than 3 in most stations. CRU has high accuracy in estimating rainfall in the eastern and northern parts of the country, with R values around 0.81, EF > 0.5, NRMSE < 2, and Bias between -2 and 6 mm. Additionally, CRU has high accuracy in estimating minimum and maximum temperatures in Iraq, with R values > 0.96, R2 > 0.95, EF > 0.95, Slope > 0.95, and NRMSE < 1.5 in most regions. Thus, GPCC and CRU data can be introduced as reliable sources for analyzing rainfall and temperature patterns, suitable for use in regions lacking data in Iraq, and suitable for water management planning and climate change adaptation.
5. Acknowledgement & Funding
The manuscript did not receive a grant from any organization
6. Conflict of Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
