Heatwaves — they’re a regular risk of summer. But this year has seen a rash of particularly vicious and anomalous instances. As the Arctic baked under numerous heatwaves in which temperatures shattered the 90 degree (Fahrenheit) mark, as the US experienced some of its worst southwestern heat ever recorded, as the UK experienced record summer heat and wildfires, and as Spain sweltered as temperatures soared above 40 degrees C (above 104 F), China was experiencing its own version of a global warming amplified scorcher.
The worst heatwave in 140 years smothered about 1/3 of China, a sprawling area covering about 3 million square miles. At the heat epicenter, Shanghai, a region inhabited by 23 million people, saw daytime temperatures above 35 degrees C (95 F) for more than 25 days during July of 2013. On July 26th, Shanghai experienced an all-time record high of 106 degrees Fahrenheit (42 C), a level not reached since record keeping began in 1873.
Shanghai also reported ten deaths and far more numerous heat injuries for the month, as the hot weather intensified this Wednesday, while dozens of deaths have been reported over a large, scorched area of south-coastal China.
Throughout this week, China has been issuing its second highest national heat alert. This level requires the establishment of a 24 hour emergency operations center in order to provide emergency response and support capabilities for the hardest hit areas. The highest alert level is so extreme that China has never used it. Unfortunately, as the human-caused warming trend continues, it seems ever more likely that such a high heat category will have to be put in use.
Those living in Hangzhou, a region located about 100 miles to the southwest of Shanghai, may have already thought officials should have used such a marker as temperatures soared to above 104 degrees Fahrenheit (40 degrees C), for six out of seven days over the past week. Meanwhile, Xiaoshan saw a new all-time record high temperature of 108 degrees Fahrenheit (42.2 degrees C) on Tuesday. The coastal city of Ningbo saw temperatures hit 109 degrees F on July 26th, the highest temperature ever recorded for a coastal city in all of South-East Asia.
In what has become a kind of macabre ritual in widening areas of the world affected by extreme heat, Chinese residents laid out shrimp and eggs to fry over scorching road surfaces. More ominously, the extreme heat threatened crops even as it baked rivers and lakes setting off massive fish kills from heat and anoxia. In some regions, the fish kills were so extreme that an estimated 60 percent of all fish were lost (normal summer heat may result in 5-10 percent fish losses in affected regions).
In order to protect crops and fish, China has engaged in a cloud seeding effort in hopes of spurring rainfall over scorched areas while it is urging localities and fish farmers to pump new water into ponds and rivers to enhance oxygen levels and reduce fish losses.
Heat dome, coastal flow, very high wet bulb temperatures
(Image source: Lance-Modis)
A dome of hot, moist air has persisted over this region for nearly a month now. Though rainfall and even flooding events have occurred due to a flow of Pacific moisture over the area and the occasional onrush of tropical cyclones, these rainfall events have done little to alleviate a combination of oppressive heat and humidity.
Flows off the ocean would normally help to somewhat alleviate the heat, but an area of typically hot summer water is now showing readings 1-2 degrees Celsius above average. This broad region of hotter than normal surface ocean waters off China now show temperatures higher than 30 degrees Celsius (86 degrees Fahrenheit). Windflows issuing off these extraordinarily hot ocean surface areas are not very helpful in cooling the baking land. Worse still, the heat dome conditions — stifling airflow, concentrating heat and locking in place a layer of heat amplifying haze and smog — have persisted for much of the past month. This combination of less effective ocean cooling and heat dome conditions has resulted in a terribly severe heatwave for this coastal region.
Coastal heatwaves are particularly oppressive and potentially lethal due to the fact that humidity tends to remain higher than in more arid regions. A wet bulb temperature above 35 degrees Celsius (95 Fahrenheit) is considered lethal for human beings. Those living in Southeast Asia are well used to living under sweltering conditions of high heat and humidity. But as temperatures approach this human threshold (25 C + wet bulb temperature), even those acclimated are at increased risk. So both extreme heat and high humidity likely contributed to the sad and tragic dozens of instances in which lives were lost during this particular event.
The forecast for Shanghai next week calls for continuing record heatwave conditions with high temperatures ranging from 99 to 102 degrees (Fahrenheit) from Sunday through Saturday. With humidity levels near 50% this means wet bulb temperatures will approach 29-30 degrees Celsius during the hottest portions of the day. This continuation of a scorching summer heat wave will result in high risk of both heat injury and loss of life for those living in this sweltering region. With little to no relief in the forecast, this section of China is likely to remain under the fire of human-caused heating as August advances.