Time series Analysis

To calculate the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) using the SPEI package in R, you need precipitation data for SPI and both precipitation and potential evapotranspiration (PET) data for SPEI. PET can be calculated using the Thornthwaite method, which requires temperature data and location latitude. After calculating PET, the water balance (precipitation minus PET) is used to compute the SPEI. The SPEI function then standardizes this water balance over a specified time scale to determine drought severity.

This figure illustrates the outcomes of the change point detection analysis conducted on monthly rainfall data across multiple stations. The analysis employed several statistical tests to identify significant shifts in the rainfall patterns over time. The figure, prepared using R, visually represents the detected change points, highlighting periods where significant shifts in monthly rainfall were observed. The data analysis was executed using Khronostat software, ensuring comprehensive application of the aforementioned statistical methods (Akter et al., 2023).

I was analyzing discharge timeseries data by preparing a wavelet graph to examine trends and variability. This approach allowed me to identify patterns and fluctuations in the data over different time scales, providing insights into both long-term trends and short-term variations.

I created time-series graphs showing temporal changes and trends for both EVI and LAI across seven clusters in Cox's Bazar from 2005 to 2023. The clusters include locations such as Nazir Tech, West Cox's Bazar Cricket Stadium, and Reju Khal outlet south. These graphs reveal distinct vegetation trends within each cluster, providing insights into environmental variability and land use patterns over the study period (Biswas et al., 2024).

The LAI density trends of Bhasan Char Island between 2015 and 2023 show significant temporal changes, indicating shifts in vegetation coverage over time. These variations highlight the dynamic nature of the island's ecosystem and provide insights into environmental factors influencing vegetation growth during this period. (Biswas et al., 2024).