Varied Solar Irradiance across North America in March: A Tale of Regional Disparities

March painted a contrasting picture of solar irradiance across North America. While the US South, Central America, and parts of the Midwest reveled in substantial increases in irradiance, other regions faced a different scenario.

The US South and Midwest witnessed a remarkable surge in irradiance, far exceeding the typical levels for March. In southern Texas, the irradiance soared to an impressive 30% above the average, outshining many other areas. Vast stretches of the southern states also experienced significant growth, with irradiance increases of 20% or more. Even regions that seemed to have a more modest increase still recorded irradiance anomalies ranging from 10% to 20% above the climatological norms. This spell of clear skies, unfortunately, came hand in hand with a significant drop in precipitation, exacerbating the already pressing drought concerns in the Great Plains. March is usually a month of transition, prone to fluctuations, but this year, the region was particularly dynamic. High temperatures and frequent storm formations created an environment that fostered persistent sunshine over the formation of clouds, driven by moisture.

In stark contrast, a large portion of the US West and Canada endured lower-than-average solar irradiance. In the southern parts of this region, most areas saw irradiance levels 10% below the average, and in some northern areas, the decline was as steep as 20%. Canada was hit particularly hard, with Quebec experiencing anomalies that approached 30% below the average. Atmospheric pressure patterns indicated the presence of a colder and stormier air mass over the northern US and Canada, triggered by a dip in the jet stream. This atmospheric configuration allowed moisture from the Pacific to penetrate deep into the continent's interior, leading to extensive cloud cover. In the Atlantic, the strong Azores high and a potentially positive phase of the North Atlantic Oscillation (NAO) likely influenced the situation by redirecting storm tracks and reinforcing the persistent cloud cover over the northeastern region.

Central America, on the other hand, was blessed with generally clear skies. The entire region enjoyed irradiance slightly above the average, with northeastern Mexico standing out with a notable spike of 30% above the March norm. This increase seems to be associated with the high-pressure system over the Pacific, which ushered in northerly winds that channeled dry air from the Chihuahuan Desert southward.

Analysis using the Solcast API revealed that this month's pattern of irradiance across North America was a result of a continental divide. Storm activities on the West coast suppressed irradiance, while high-pressure systems maintained clear and dry conditions in the East. Solcast's data, derived from tracking clouds and aerosols at a resolution of 1-2km globally through satellite data and proprietary AI/ML algorithms, provides a detailed and accurate picture of these irradiance variations, which is crucial for the operations of over 350 companies managing more than 300 GW of solar assets worldwide.