Discussion: A National Institute of Health (NIH) study performed in 2013 indicated flu virus spreads more easily in climate conditions during wintertime that are cold and dry or cool and wet. The COVID-19 outbreak began in Wuhan, China located in the east-central portion of the country. The climate pattern across China including the Wuhan area has been unusually wet during meteorological winter (Fig. 1). The precipitation rate analysis by NCDC/PSD estimates a large area of approximately 4-8 in. of rain above normal for central and eastern China. The unusually wet pattern is attributed to a climate pattern in the Indian Ocean known as the Indian Ocean Dipole. The positive phase of the Indian Ocean Dipole was historic last October. Since that time the +IOD pattern has weakened. However, the lag effect of this intense climate influence has contributed significantly to the wet winter pattern across China.
Fig. 1: Using the precipitation rate analysis for the past 90 days across China a wetter than normal climate is revealed.