One of the most important analysis in many hydrological and agricultural studies is to convert the daily rainfall data into sub-daily (hourly) because in many rainfall stations, only the daily rainfall data are available and for a comprehensive rainfall analysis, these data should be converted to sub-daily. Many experimental and analytical methods are available for this conversion but one of the simplest yet accurate ones has been proposed by the Indian Meteorological Department (IMD). Since the IMD method has shown low accuracy in some regions, in this study, the IMD method is modified to a single parameter equation, called Modified Indian Meteorological Department (MIMD) in order to improve the accuracy of the conversion. For this reason, the parameter is calibrated so that the maximum correlation between observed and estimated values is achieved. Five stations in different regions with different climatic conditions were selected so that the daily and sub-daily rainfall data were available in each of them. Then, the parameter of the MIMD method was derived for each station. The results were compared with both observed data and IMD method and it was shown that the mean correlation coefficient of MIMD and IMD methods were 0.9 and 0.73 respectively for 12-h rainfall depth which indicated that the accuracy of the MIMD method in estimation of sub-daily rainfall depths was significantly increased. Moreover, the results showed that the accuracy of the MIMD method decreases as rainfall duration decreases.

许多水文和农业研究中最重要的分析之一是将日降雨数据转换为次日（每小时），因为在许多降雨站中，只有日降雨数据可用，对于综合降雨分析，这些数据应该是转换为亚日。许多实验和分析方法可用于这种转换，但印度气象部门 (IMD) 提出了一种最简单但准确的方法。由于IMD方法在一些地区表现出较低的精度，本研究将IMD方法修改为单参数方程，称为修改印度气象部门（MIMD），以提高转换精度。为此，参数被校准，以便实现观测值和估计值之间的最大相关性。选择了不同气候条件下不同地区的五个站点，以便每个站点都可以获得日和次日降雨量数据。然后，为每个站导出 MIMD 方法的参数。将结果与实测数据和IMD方法进行了比较，结果表明，MIMD和IMD方法对于12h降雨深度的平均相关系数分别为0.9和0.73，表明MIMD方法在估计亚降水量方面的准确性。日降雨深度明显增加。此外，结果表明 MIMD 方法的准确性随着降雨持续时间的减少而降低。选择了不同气候条件下不同地区的五个站点，以便每个站点都可以获得日和次日降雨量数据。然后，为每个站导出 MIMD 方法的参数。将结果与实测数据和IMD方法进行了比较，结果表明，MIMD和IMD方法对于12h降雨深度的平均相关系数分别为0.9和0.73，表明MIMD方法在估计亚降水量方面的准确性。日降雨深度明显增加。此外，结果表明 MIMD 方法的准确性随着降雨持续时间的减少而降低。选择了不同气候条件下不同地区的五个站点，以便每个站点都可以获得日和次日降雨量数据。然后，为每个站导出 MIMD 方法的参数。将结果与实测数据和IMD方法进行了比较，结果表明，MIMD和IMD方法对于12h降雨深度的平均相关系数分别为0.9和0.73，表明MIMD方法在估计亚降水量方面的准确性。日降雨深度明显增加。此外，结果表明 MIMD 方法的准确性随着降雨持续时间的减少而降低。将结果与实测数据和IMD方法进行了比较，结果表明，MIMD和IMD方法对于12h降雨深度的平均相关系数分别为0.9和0.73，表明MIMD方法在估计亚降水量方面的准确性。日降雨深度明显增加。此外，结果表明 MIMD 方法的准确性随着降雨持续时间的减少而降低。将结果与实测数据和IMD方法进行了比较，结果表明，MIMD和IMD方法对于12h降雨深度的平均相关系数分别为0.9和0.73，表明MIMD方法在估计亚降水量方面的准确性。日降雨深度明显增加。此外，结果表明 MIMD 方法的准确性随着降雨持续时间的减少而降低。