H1B specifically represents the PDSI value for a 12-month time period, which is commonly used to assess drought conditions over a longer-term scale compared to shorter periods like H1 or H2 (3-month and 6-month time periods, respectively). The H1B value provides insights into the overall hydrologic conditions and potential drought severity over the past year.
The PDSI is calculated based on a water balance approach that considers precipitation, temperature, and soil moisture. It ranges from extremely wet to extremely dry conditions, with negative values indicating drought and positive values indicating wetness. The H1B value, therefore, represents the cumulative water balance over the 12-month period and can be used to assess the intensity and duration of drought or wet conditions during that time frame.
Hydrologists and water resource managers use the PDSI, including the H1B value, to monitor drought conditions, assess the impacts of drought on ecosystems and water supplies, and make informed decisions related to water management and drought mitigation strategies.