TAU Study Explains Mistakes in Weather Forecasting

Groundhog forecast

A new study from researchers at Tel Aviv University explains why sometimes the weather experts get it wrong. This is especially significant today given how little of the expected snow actually fell on New York earlier this week in the great American blizzard of 2015.

Research published in the journal Land by Prof. Pinhas Alpert of the Department of Geophysics, Atmospheric and Planetary Sciences at TAU’s Raymond & Beverly Sackler Faculty of Exact Sciences prioritizes, for the first time, reasons for forecast failures across different regions of the world. Using multi-regression-based statistics on data collected between 1979-1993 on tens of thousands of forecast points, Prof. Alpert and his team were able to quantify the causes — man-made and natural — for weather prediction inaccuracies.

“Considering my background in forecasting, weather prediction fallacies bothered me for a long time, ” said Prof. Alpert. “Since joining TAU in 1982, I have been looking for a way to quantify the dominant factors that cause errors in forecasting. Until now, there has been no comprehensive analysis of these factors. They have been studied separately, but not in combination. I decided to quantify and prioritize the dominant factors for different regions, and provide this valuable information to the world scientific community.”

Using statistical analysis of meteorological data over thousands of locations and the course of 15 years, Prof. Alpert identified unique factors affecting forecasts in Europe, North Africa, the Mediterranean, Asia, and East Asia. The researchers found the dominant factors clouding the accuracy of predictions comprised land-use changes (i.e. an area that had been covered in forest is suddenly bare), topography, particles in the atmosphere and population density.

“For example, when Israel’s national water pipeline crossed the northern Negev in June 1964, it changed the lay of the land, ” said Prof. Alpert. “After a relatively short period of time, the desert was blooming, affecting the generation of clouds, precipitation, and temperature extremes. It is difficult for forecasters to incorporate changes like this. In effect, this single land-cover change altered the entire local climate over the Northern Negev, and existing forecast models had difficulty accommodating this, leading to erroneous predictions.”

“The only tool the weather forecaster has is his model, and the only choice he or she has is to look at different models, each of which has strengths and weaknesses, ” said Prof. Alpert. “Several hundred research groups are trying to improve forecasting models all the time. These groups also seek to improve predictions of climate change and global warming. Our study provides them with information about the right topics of research to address for each region.”

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