Urban-climate interactions during summer over eastern North America

Abstract

The urban heat island is a representative urban climate characteristic, which can affect heat-stress conditions and extreme precipitation that are closely connected with human life. Better understanding of urban-climate interactions, therefore, is crucial to ultimately support better planning and adaptation in various application elds. This study assesses urban-climate interactions during summer for eastern North America using regional climate model simulations at 0.22° resolution. Two regional climate model experiments, with and without realistic representation of urban regions, are performed for the 1981-2010 period. Comparison of the two experiments shows higher mean temperatures and reduced mean precipitation in the simulation with realistic urban representation, which can be attributed primarily to reduced albedo and soil moisture for the urban regions in this simulation. Furthermore, the mean temperature and precipitation in the simulation with improved urban representation is also closer to that observed. Analysis of short-duration precipitation extremes for climatologically different sub-regions, however, suggests that, for higher temperatures, the magnitudes of precipitation extremes are generally higher in the simulation with realistic urban representation, particularly for coastal urban regions, and are collocated with higher values of convective available potential energy and cloud fraction. Enhanced sea and lake breezes associated with lower sea level pressure found around these regions, contribute additional water vapor and further enhance dynamic convective development, leading to higher precipitation intensities. Analysis of temperature extremes clearly demonstrates that urban regions experience aggravated heat-stress conditions due to relatively higher temperatures despite reduced relative humidity. Double the number of extreme heat spells lasting six or more days are noted for the coastal urban regions in the study domain. This study, in addition to demonstrating the differences in urban-climate interactions for climatologically different regions, also demonstrates the need for better representation of urban regions in climate models to generate realistic climate information.

Interplay Between Urbanization and Irrigation on Summer Climate in the Huang‐Huai‐Hai Plain, China

“…Although urbanization is more likely to influence T2min than T2max in some studies (Hamdi et al, 2020), it dramatically decreased the LE in 3HP. A higher average temperature and less precipitation are noticed in urbanization regions in northern America during summer (Oh & Sushama, 2021). Note.…”

“…Case 3 -Case 2 was applied to quantify the climatic impact of irrigation and Case 3 -Case 1 was handled to investigate the combined effect of irrigation and urbanization on the summer climate in 3HP. All simulations in this study were performed during the growing summer season (JJA) when the urban climate interactions are more predominant (Oh & Sushama, 2021). All simulation groups covered a 19-summer period from 00:00 UTC on June 1st to 24:00 UTC on August 31st from 2000 to 2018.…”

“…However, the ability of ALARO-SURFEX to simulate the impact of urbanization and irrigation has not been estimated yet over 3HP. A better representation of urbanization regions in climate models is essential to generate realistic climate information (Oh & Sushama, 2021). Furthermore, the effects of urbanization and irrigation were analyzed individually in most previous studies (T. Chen et al, 2020;X.…”

Quantification of The Performance of CMIP6 Models for Dynamic Downscaling in The North Pacific and Northwest Pacific Oceans

“…It implies that ERA5 data is potentially more suitable for evaluating regional climate variability. Numerous studies have used ERA5 data as a reference for the reproducibility of global climate models with near-surface variables (e.g., Kim et al 2020;Li et al 2021;Oh and Sushama 2021). To evaluate the estimated ocean heat content and vertical profile of seawater potential temperature, the Institute of Atmospheric Physics (IAP) ocean temperature data for the period 1979-2014 is collected (e.g., Cheng et al 2017).…”

“…Dynamic downscaling, such as a regional ocean-climate model (RCM), is a powerful tool that provides regional climate information on higher spatial and temporal resolutions than those of global reanalysis and climate models, and it is particularly useful for determining processes related to complex coastal terrain (e.g., Seo et al 2014;Teufel et al 2017;Zhang et al 2020;Oh and Sushama 2021). Considerable work has been conducted to improve RCM-based climate information by developing dynamical and physical schemes that are more sophisticated (e.g., Giorgi et al 2012;Lindstedt et al 2015;Komkoua Mbienda et al 2021).…”