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Sunday, July 14, 2024

Scorching nights in Pyongyang: Heatwave grips city amid climate change

As climate change intensifies, global temperatures are rising at an alarming rate. Recent reports indicate extreme heat waves, with temperatures soaring to 52 degrees Celsius in some regions. Tragically, hundreds or possibly thousands of heat-related deaths have been reported in India and Saudi Arabia.

Even though it is only June, the Korean Peninsula is already experiencing “tropical nights” – a phenomenon where nighttime temperatures remain above 25 degrees Celsius. This year’s heat has arrived earlier than usual, with June breaking records for humidity levels.
But what about the temperature conditions in Pyongyang, the capital of North Korea?

Thermal infrared imagery provides clues to temperature distribution in Pyongyang

To answer this question, I conducted an analysis using satellite data to examine the potential distribution of tropical nights across different administrative units in the capital. The study utilized thermal infrared data captured by NASA’s Landsat-8 satellite.

My analysis revealed that tropical nights occur in 15% of Pyongyang’s area. While the wooded outskirts of Kangdong County showed low terrestrial heat, surface temperatures were notably high in open fields and densely built urban areas. These findings underscore the importance of increased tree planting to mitigate global warming effects.

This distribution chart of “tropical nights” (a night when the temperature does not drop below 25 degrees Celsius) for each district of Pyongyang derives from an analysis of thermal infrared data. The wooded ridges are found to have less terrestrial heat, and the open fields and dense downtown area are found to have higher levels of heat. Image=Landsat-8 (thermal infrared)

I examined temperature distribution and tropical night occurrence in Pyongyang using thermal infrared imagery (100-meter resolution) from the Landsat-8 satellite, captured around 11 AM on June 17. At that time, Pyongyang’s average temperature was 27°C, with a range of 17°C to 38°C.

For my analysis of tropical nights, I used the following methodology:

  • I defined a tropical night as one where the lowest overnight temperature is 25°C or above.
  • Using Seoul as a reference (as of June 18), I observed that the overnight low of 24°C at 4-6 am was 6°C lower than the 11 AM temperature of 30°C.
  • Acknowledging potential variations due to season, month, or date, I assumed a consistent 6°C difference between the nighttime low and 11 am temperature.
  • Based on this assumption, I deduced that a nighttime low of 25°C or higher (the tropical night threshold) would correspond to an 11 AM temperature of 31°C or higher.

Therefore, I hypothesized that areas in Pyongyang with temperatures between 31°C and 38°C at 11 AM on June 17 were likely experiencing tropical nights.

The Landsat satellite, equipped with a thermal sensor, captures images at 11 AM. As no thermal infrared satellites can take nighttime images, I analyzed hypothetical tropical nights based on daytime data.

In my Pyongyang temperature analysis, I marked areas with temperatures between 31-38°C as tropical night zones in red. Other areas were color-coded at two-degree intervals.

My hypothetical tropical night distribution chart showed these conditions occurring in dense urban areas, including Central District (location of Kim Il Sung Square) and Mangyongdae District. On the city outskirts, a broad red swath indicating tropical nights stretched across Sadong, Ryokpo, and Samsok districts, as well as Kangnam and Kangdong counties. High-temperature areas were also scattered across other administrative units.

I conducted a similar analysis for Seoul using June 18 thermal infrared data. While detailed results aren’t included here, Seoul’s average temperature at 11 AM was 30°C, ranging from 19°C to 40°C, indicating considerably muggier conditions than Pyongyang. This difference is likely due to Seoul’s lower latitude. It’s worth noting that Pyongyang’s area (174,770 hectares) is nearly three times that of Seoul (60,521 hectares).

Pyongyang nights feel hotter due to lack of air conditioning

North Korean defectors report that despite North Korea’s higher latitude and generally lower temperatures, the lack of climate control in buildings makes hot weather feel more intense there. In contrast, South Koreans can use air conditioning to combat summer heat, sometimes even worrying about overcooling.

In North Korea, air conditioning is scarce, and even fans are rarely used due to irregular power supply. For North Koreans today, staying cool in summer often means resorting to methods familiar to older generations: handheld fans, tree shade, or dunking one’s head in well water.

The tropical night distribution area and ratio were calculated for each district of Pyongyang. Ryokpo District was found to be the muggiest by day and night, followed by Kangdong County and Samsok District. Data=Landsat-8 (thermal infrared analysis)

I analyzed tropical night distribution across Pyongyang’s administrative units. Tropical nights were observed in 26,022 hectares, or 14.9% of Pyongyang’s total area. Ryokpo District and Kangdong County had the most extensive tropical night areas, each exceeding 50,000 hectares, followed by Sadong District, Kangnam County, Mangyongdae District, and Hyongjesan District.

Ryokpo District was particularly prone to tropical nights, with high terrestrial heat in 47.4% (5,523 hectares) of its total area (11,643 hectares). This suburban district, with more open areas than dense ones, showed high surface heat levels. Open fields without tree cover appear to reflect more direct sunlight, increasing terrestrial heat.

In contrast, eastern Kangdong County showed a long green band (indicating lower temperatures) along wooded hills, demonstrating how forests and hills can mitigate summer heat. The coolest surface area was the Taedong River.

For researchers interested in my methodology, I used ArcGIS software and followed a six-step procedure derived from extensive literature review. I’ve omitted technical details here but can provide specifics upon request. Note that Landsat-9 data would require different constants.

It’s important to note that temperatures derived from this thermal infrared analysis may vary from actual temperatures by ±3 degrees. Precise measurements require ground-level thermometers.

This article presents an unconventional, hypothetical analysis of tropical nights in Pyongyang using daytime satellite thermal infrared data. While unconventional, such “backward thinking” can lead to novel approaches and insights. I welcome reader feedback on this experimental research and analysis method.

Read in Korean

July 04, 2024 at 06:30AM

by DailyNK(North Korean Media)

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