The Evolving Distribution of Relative Humidity Conditional Upon Daily Maximum Temperature in a Warming Climate

The impacts of heat waves in a warming climate depend not only on changing temperatures but also on changing humidity. Using 35 simulations from the Community Earth System Model Large Ensemble (CESM LENS), we investigate the long-term evolution of the joint distribution of summer relative humidity (RH) and daily maximum temperature (Tmax) near four U.S. cities (New York City, Chicago, Phoenix, and New Orleans) under the high-emissions Representative Concentration Pathway (RCP) 8.5. We estimate the conditional quantiles of RH given Tmax with quantile regression models, using functions of temperature for each city in July for three time periods (1990–2005, 2026–2035, and 2071–2080). Quality-of-fit diagnostics indicate that these models accurately estimate conditional quantiles for each city. As expected, each quantile of Tmax increases from 1990–2005 to 2071–2080, while mean RH decreases modestly. Conditional upon a fixed quantile of Tmax, the median and high quantiles of RH decrease, while those of the Heat Index (HI) and dew point both increase. This result suggests that, despite a modest decrease in median relative humidity, heat stress measured by metrics considering both humidity and temperature in a warming climate will increase faster than that measured by temperatures alone would indicate. For a fixed Tmax, the high quantiles of RH (and thus of HI and dew point) increase from 1990–2005 to 2071–2080 in all four cities. This result suggests that the heat stress of a day at a given Tmax will increase in a warming climate due to the increase of RH

Amplified subtropical stationary waves in boreal summer and their implications for regional water extremes

The linkage between climate change and increased frequency/magnitude of weather extremes remains an open question in the scientific field. Here we investigate such a dynamical linkage by focusing on an amplification trend of the northern subtropical stationary waves found in recent decades. Specifically, we show that in multiple modern reanalysis products, a robust positive trend exists in a wave amplitude index defined through the summer-mean tropospheric stream function field. Pronounced changes in the subtropical atmospheric circulation accompany this wave amplification, including an intensified South Asian monsoon and strengthened subtropical highs over the North Pacific and North Atlantic oceans. Through modifying the characteristics of large-scale moisture transport, these circulation changes are coupled to changes in the regional precipitation amount and the occurrence of water extremes including both droughts and heavy rainfall events. Given this connection, amplified stationary waves have likely contributed to the elevated occurrence probabilities of droughts in the central United States, Mexico, Japan, and northern China, as well as those of heavy rainfall events in South Asia, southeastern China, and the eastern United States. These results suggest that as climate warming continues, the amplification of subtropical stationary waves will increase the risk of water extremes over the above-mentioned regions

Escalating global exposure to compound heat-humidity extremes with warming

Heat stress harms human health, agriculture, the economy, and the environment more broadly. Exposure to heat stress is increasing with rising global temperatures. While most studies assessing future heat stress have focused on surface air temperature, compound extremes of heat and humidity are key drivers of heat stress. Here, we use atmospheric reanalysis data and a large initial-condition ensemble of global climate model simulations to evaluate future changes in daily compound heat-humidity extremes as a function of increasing global-mean surface air temperature (GSAT). The changing frequency of heat-humidity extremes, measured using wet bulb globe temperature (WBGT), is strongly related to GSAT and, conditional upon GSAT, nearly independent of forcing pathway. The historical ∼1°C of GSAT increase above preindustrial levels has already increased the population annually exposed to at least one day with WBGT exceeding 33°C (the reference safety value for humans at rest per the ISO-7243 standard) from 97 million to 275 million. Maintaining the current population distribution, this exposure is projected to increase to 508 million with 1.5°C of warming, 789 million with 2.0°C of warming, and 1.22 billion with 3.0°C of warming (similar to late-century warming projected based on current mitigation policies)

The East Pacific Wavetrain: Its variability and impact on the atmospheric circulation in the boreal winter

The East Pacific wavetrain (EPW) refers to here the intense stationary wave activity detected in the troposphere over the East Pacific and North America in 45 northern winters from 1958 to 2002. The EPW is generated in the lower troposphere over the East Pacific, propagating predominantly eastward into North America and slightly upward then eventually into the stratosphere. The intensity of the EPW varies from year to year and exhibits apparent decadal variability. For the period 1958-1964, the EPW was in its second maximum, and it was weakest for the period 1965-1975, then it was strongest for the period 1976-1987. After 1987, the EPW weakened again. The intensity and position of the members (i.e., the Aleutian low, the North American trough, and the North American ridge) of the EPW oscillate from time to time. For an active EPW versus a weak EPW, the Aleutian low deepens abnormally and shifts its center from the west to the east of the date line, in the middle and upper troposphere the East Asian trough extends eastward, and the Canadian ridge intensifies at the same time. The opposite is true for a weak EPW. Even in the lower stratosphere, significant changes in the stationary wave pattern are also observed. Interestingly the spatial variability of the EPW assumes a Pacific-North American (PNA)-like teleconnection pattern. It is likely that the PNA low-frequency oscillation is a reflection of the oscillations of intensity and position of the members of the EPW in horizontal direction.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000303058800005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Meteorology & Atmospheric SciencesSCI(E)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)5ARTICLE3471-4832

Wetbulb Globe Temperature

<p>This dataset contains simplified WetBulb Globe Temperature (WBGT) at hourly frequency spanning from 1979 to 2022. The variables utilized for WBGT calculation include dry-bulb temperature, humidity, and surface pressure obtained from the ERA5 reanalysis. First, an isobaric wet-bulb temperature (Tw) is computed using these variables. Then the simplified WBGT is determined through the formula WBGT*= 0.7Tw+0.3Td. More details are described in "Dawei Li*, Jiacan Yuan*, and Robert E. Kopp (2020): Escalating global exposure to compound heat-humidity extremes with warming. <em>Environmental Research Letters</em>. DOI:10.1088/1748-9326/ab7d04". Please cite this article when using this dataset.</p> <p>WBGT-ERA5-v2.0 is an updated version for WBGT-ERA5-v1.1. In the version of WBGT-ERA5-v1.1, an assumption was made that RH = q/qs, where saturation specific humidity (qs) was considered equal to the saturation mixing ratio rs. In the version of WBGT-ERA5-v1.2, we calculate RH and qs exactly following their original definitions: RH = e/es (where e is vapor pressure and es is saturated vapor pressure), and qs = rs/(1+rs). The updates will slightly improve the precision of the wet-bulb temperature estimation under high-temperature condition  </p>This project is supported by National Natural Science Foundation of China (Grant No. 42175066), Shanghai Municipal Natural Science Fund (20ZR1407400) and Shanghai Pujiang Program (Grant No. 20PJ1401600)

The influence of humid heat on morbidity of megacity Shanghai in China

Background: Increased attention has been paid to humid-heat extremes as they are projected to increase in both frequency and intensity. However, it remains unclear how compound extremes of heat and humidity affects morbidity when the climate is projected to continue warming in the future, in particular for a megacity with a large population. Methods: We chose the Wet-Bulb Globe Temperature (WBGT) index as the metric to characterize the humid-heat exposure. The historical associations between daily outpatient visits and daily mean WBGT was established using a Distributed Lag Non-linear Model (DLNM) during the warm season (June to September) from 2013 to 2015 in Shanghai, a prominent megacity of China. Future morbidity burden related to the combined effect of high temperature and humidity were projected under four greenhouse gases (GHGs) emission scenarios (SSP126, SSP245, SSP370 and SSP585). Results: The humid-heat weather was significantly associated with a higher risk of outpatient visits in Shanghai than the high-temperature conditions. Relative to the baseline period (2010–2019), the morbidity burden due to humid-heat weather was projected to increase 4.4 % (95 % confidence interval (CI): 1.1 %–10.1 %) even under the strict emission control scenario (SSP126) by 2100. Under the high-GHGs emission scenario (SSP585), this burden was projected to be 25.4 % (95 % CI: 15.8 %–38.4 %), which is 10.1 % (95 % CI: 6.5 %–15.8 %) more than that due to high-temperature weather. Our results also indicate that humid-hot nights could cause large morbidity risks under high-GHGs emission scenarios particularly in heat-sensible diseases such as the respiratory and cardiovascular disease by the end of this century. Conclusions: Humid heat exposures significantly increased the all-cause morbidity risk in the megacity Shanghai, especially in humid-hot nights. Our findings suggest that the combined effect of elevated temperature and humidity is projected to have more substantial impact on health compared to high temperature alone in a warming climate

Heatwaves, medications, and heat-related hospitalization in older Medicare beneficiaries with chronic conditions.

BackgroundHeatwaves kill more people than floods, tornadoes, and earthquakes combined and disproportionally affect older persons and those with chronic conditions. Commonly used medications for chronic conditions, e.g., diuretics, antipsychotics disrupt thermoregulation or fluid/electrolyte balance and may sensitive patients to heat. However, the effect of heat-sensitizing medications and their interactions with heatwaves are not well-quantified. We evaluated effects of potentially heat-sensitizing medications in vulnerable older patients.MethodsUS Medicare data were linked at the zip code level to climate data with surface air temperatures for June-August of 2007-2012. Patients were Medicare beneficiaries aged ≥65 years with chronic conditions including diabetes, dementia, and cardiovascular, lung, or kidney disease. Exposures were potentially heat-sensitizing medications including diuretics, anticholinergics, antipsychotics, beta blockers, stimulants, and anti-hypertensives. A heatwave was defined as ≥2 days above the 95th percentile of historical zip code-specific surface air temperatures. We estimated associations of heat-sensitizing medications and heatwaves with heat-related hospitalization using self-controlled case series analysis.ResultsWe identified 9,721 patients with at least one chronic condition and heat-related hospitalization; 42.1% of these patients experienced a heatwave. Heatwaves were associated with an increase in heat-related hospitalizations ranging from 21% (95% CI: 7% to 38%) to 33% (95% CI: 14% to 55%) across medication classes. Several drug classes were associated with moderately elevated risk of heat-related hospitalization in the absence of heatwaves, with rate ratios ranging from 1.16 (95% CI: 1.00 to 1.35) to 1.37 (95% CI: 1.14 to 1.66). We did not observe meaningful synergistic interactions between heatwaves and medications.ConclusionsOlder patients with chronic conditions may be at heightened risk for heat-related hospitalization due to the use of heat-sensitizing medications throughout the summer months, even in the absence of heatwaves. Further studies are needed to confirm these findings and also to understand the effect of milder and shorter heat exposure