# A Critical Assessment of the Recent Rapid Decline in Land Surface Relative Humidity

> **NSF 01002526DB NSF RESEARCH & RELATED ACTIVIT** · SUNY at Albany (NY) · $599,937

## Abstract

Surface relative humidity (RH) has major impacts on human comfort and health, as well as droughts and wildfires. Historical data show rapid declines in surface RH over many land areas since the late 1990s. Such a RH decrease enhances atmospheric demand for moisture under rising temperatures, leading to increased risk of drought and wildfires in the western U.S. and other regions. However, the exact cause of this RH decrease is unknown. Given the broad impacts of surface RH, improved understanding of the RH decline is critically important. This project will help explain the rapid decline in recent surface RH, thereby benefiting research in human health, drought and wildfires in the U.S. and other regions. It will also help the PI train two graduate students, teach climate-related courses, and educate the public about our changing climate. 

A comprehensive analysis and critical assessment of the recent RH trend will be carried out to reveal its causes and assess its reliability. Utilizing the Principal Investigator's expertise in homogenizing climate records, monthly RH data series from global weather stations since 1973 will be homogenized using advanced statistical methods combined with available metadata to detect and remove discontinuities associated with instrumental changes. This will help quantify the impact of such discontinuities on the recent RH trend over land. Further, RH variations and changes will be compared with those in physically related but independently 

## Key facts

- **NSF award ID:** 2528650
- **Awardee organization:** SUNY at Albany (NY)
- **SAM.gov UEI:** NHH3T1Z96H29
- **PI:** Aiguo Dai
- **Primary program:** 01002526DB NSF RESEARCH & RELATED ACTIVIT
- **All programs:** —
- **Estimated total:** $599,937
- **Funds obligated:** $599,937
- **Transaction type:** Standard Grant
- **Period:** 09/15/2025 → 08/31/2028

## Primary source

NSF Award Search: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2528650

## Citation

> US National Science Foundation, Award 2528650, A Critical Assessment of the Recent Rapid Decline in Land Surface Relative Humidity. Retrieved via AI Analytics 2026-06-07 from https://api.ai-analytics.org/grant/nsf/2528650. Licensed CC0.

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