The severity of heat and cold waves amplified by high relative humidity in humid subtropical basins: a case study in the Gan River Basin, China

Abstract

High relative humidity (RH) and temperature extremes can occur simultaneously and persist for periods of time, resulting in serious harm to human health, especially in humid regions. Here, the Gan River Basin was used as a case study to investigate the characteristics of heat and cold waves using the apparent temperature (combined air temperature and RH) of the observed and ERA5 reanalysis datasets. Heat waves showed an increasing trend from 1961 to 2018 (particularly from 1997 to 2018), whereas during the same period, cold waves showed a signi cant decreasing trend. In general, ERA5 reasonably re ected the spatiotemporal characteristics of heat and cold waves, but the ability to simulate cold waves was greater than that of heat waves. The amplifying effect of high RH on heat waves is signi cantly greater than on cold waves. The increasing rates of heat waves in ERA5 at the three grades other than extreme heat waves were slightly greater than the observations. Cold waves at various grades showed signi cant downward trends, and the decreasing rates of cold wave in observations were slightly greater than those of ERA5. Using an analysis of the return period (occurrence probability), traditional univariate risk assessment methods based on maximum or minimum temperature may substantially underestimate the risk of extreme events, such as the 2014 heat wave or the 1969 cold wave, because the effects of RH were ignored.

The influence of water vapour on winter humidity‐related extreme cold events in China

“…Based on the CDF, HECEs are categorized into four grades: mild (50%-100%), moderate (25%-50%), severe (10%-25%) and extreme (<10%). [Colour figure can be viewed at wileyonlinelibrary.com] the normalized intensity of all the HECEs, as reported by Zhang et al (2023a). This robust association suggested that higher levels of water vapour lead to a heightened intensity of HECEs.…”

“…To consider the role of water vapour, here, a given day was identified as an HECE when the WBGT fell below the 10th percentile. The 10th percentile was calculated for each calendar day using daily WBGT within a 3-day half-window centred on the calendar day from 1959 to 2020 and smoothed by applying a 31-day moving average to eliminate highfrequency noise (He et al, 2023;Zhang et al, 2023a). For an occurrence to be classified as an HECE, it must persist for a minimum of three consecutive days to filter short events caused by local temperature fluctuations.…”

“…High relative humidity not only intensifies the thermal sensation experienced by the human body but also accentuates the perception of cold. For example, Zhang et al (2023a, 2023b) used temperature and relative humidity variables to define apparent temperature to study humid heatwaves and humid extreme cold events in the Ganjiang River basin of China, and discovered that water vapour can amplify both heat waves and ECEs. Li et al (2023) defined a precipitation index based on temperature and precipitation to investigate a wet and cold event in southern China in 2022.…”

“…Several novel metrics incorporating both temperature and humidity have been proposed in previous studies, including wet‐bulb temperature (), heat stress index (HI), apparent temperature () and wet‐bulb globe temperature (WBGT) (Li et al, 2020; Luo et al, 2022; Xu et al, 2021; Zhang et al, 2023a, 2023b). These indices take into account the effects of water vapour and temperature.…”

Quantifying Chilling Injury on the Photosynthesis System of Strawberries: Insights from Photosynthetic Fluorescence Characteristics and Hyperspectral Inversion

“…However, like many experiments involving temperature control variables, such constant sub-zero temperature scenarios are rarely encountered in actual strawberry cultivation, which often involves protective measures such as greenhouses or plastic tunnels. Lowtemperature events, such as cold waves, in major strawberry-producing regions globally typically last for no more than 10 days [30,31]. Inspired by prior research, we hypothesize that non-lethal daytime dynamic chilling exposures may have different effects on the pho-tosynthetic system activity in different photoperiod types of strawberries.…”