近日，美国罗格斯大学Ying Fan团队研究了具有横向水文流动的全球湿度指数。2025年8月6日出版的《自然》杂志发表了这项最新研究成果。

干旱指数被广泛用于表示陆地上的水资源可用性。平衡气候供水（降水，P）和需求（潜在蒸散，PET），它通常表示为P/PET比率1或湿度指数。水也通过河流和地下水横向流动，从丘陵流到山谷，从高山流到平原，补贴接收的低地。

研究组表明，这种横向补贴减少了接收低地的干旱。首先用全球水文模型估算了30个″全球网格的地表水和地下水每月补贴（Qlat）。然后，将传统的全球湿度指数（GHI）计算为P/PET，将包括qat在内的新GHI计算为(P + qat)/PET。后者被称为GHI_topo，反映陆地地形，在水文汇聚的低地较高。它还表现出延迟和潮湿的季节性（相对于P），因为延迟和不同主题的laat到达接收低地。

这种由气候和地形引起的时空特征，使GHI_topo成为下梯度社会和生态系统中当地可用水量的更现实的指标，使干旱地区和时间的生活成为可能。全球范围内，GHI_topo ≥ 1（供水量满足或超过需水量）的陆地面积比GHI ≥ 1的面积高出33%，在干旱和季节性干旱气候区这一比例则远高得多。

附：英文原文

Title: A global humidity index with lateral hydrologic flows

Author: Miguez-Macho, Gonzalo, Fan, Ying

Issue&Volume: 2025-08-06

Abstract: The aridity index is widely used to indicate water availability on land. Balancing climatic water supply (precipitation, P) against demand (potential evapotranspiration, PET), it is often expressed as the P/PET ratio1 or humidity index. Water also flows laterally by rivers and groundwater, from hills to valleys and from mountains to plains, subsidizing the receiving lowlands2. Here, we show that this lateral subsidy reduces aridity in the receiving lowlands. We first estimate monthly subsidies (Qlat) by surface and groundwater at 30″ global grids with a global hydrology model. We then calculate the conventional global humidity index (GHI) as P/PET and a new GHI including Qlat as (P+Qlat)/PET. Termed GHI_topo, the latter reflects land topography, higher in hydrologically convergent lowlands. It also exhibits a delayed and dampened seasonality (relative to P) owing to delayed and diffused Qlat arrival at the receiving lowlands. Such spatiotemporal features of Qlat, arising from both the climate and the terrain, make GHI_topo a more realistic indicator of local water availability in downgradient societies and ecosystems, enabling life in arid locations and times. Global land area with GHI_topo≥1 (supply meets or exceeds demand) is 33% greater than GHI≥1 and far higher in arid and season-arid climates.

DOI: 10.1038/s41586-025-09359-3

Source: https://www.nature.com/articles/s41586-025-09359-3