This study uses nighttime light measurements to quantify changes in nighttime lighting and the refugee population in Ukraine before and after Russia’s invasion. The authors also evaluate the effectiveness of these new methods for estimating refugee population changes during the war.
The authors employed a logistic equation to construct a model of nighttime lights and refugee population fluctuations. Nighttime light data were obtained from the Day–Night Band (DNB) sensor of the VIIRS onboard the S-NPP and Joint Polar Satellite System (JPSS) satellite platforms and were analyzed in combination with UNHCR data on Ukrainian refugees.
Main results:
- One week after the Russian invasion of Ukraine, the nighttime light area and the average nighttime light in Ukraine declined steeply. In the first week following the outbreak of the war in Ukraine, the national nighttime light area fell by 50 percent, and by the fifth week, the nighttime light area had fallen by 75 percent, indicating widespread destruction. Various measures of the intensity of nighttime light also declined substantially. The changes in nighttime lights were especially pronounced in and around Kyiv and the northern and eastern regions.
- Changes in the refugee population calculated through models and nighttime light data were mostly consistent with UNHCR data. The authors found a strong correlation between the registered refugee population and nighttime lights.
The analysis reveals a substantial decline in nighttime light area and intensity across Ukraine, which is correlated with increases in the refugee population. Estimates of changes in the refugee population based on nighttime lights data were largely consistent with actual UNHCR data, suggesting that nighttime light data could be used to complement or triangulate traditional sources of data on refugee flows.