Name
Honorary Doctorate Jón Egill Kristjánsson
Department of Geosciences, University of Oslo, Norway

Title
Hunting High for Polar Lows

Time and place
Thu 26 Sep 2013, 11.15
Room C609, Arrhenius Laboratory, 6th floor

(This event has taken place).

 

Abstract
Despite recent advances in numerical weather prediction (NWP), polar lows still represent a major forecasting challenge. This is due to a combination of factors: Polar lows form over data sparse regions, they are an order of magnitude smaller than synoptic-scale cyclones, and they are partly driven by moist convection, which is often inadequately treated in operational NWP models. Polar lows form in connection with marine cold air outbreaks over relatively warm seas during the winter, e.g., over the Norwegian Sea, the Barents Sea, the Denmark Strait and the Sea of Okhotsk, as well as near Antarctica.

In this talk, we will present some highlights from a 3-week aircraft-based measurement campaign out of Andøya (69°N, 16°E) in 2008, as well as its follow-up including the development of a limited area ensemble prediction system at the Norwegian Meteorological Institute. During the campaign, which was a part of the IPY-THORPEX project (Kristjánsson et al., 2011; BAMS), three significant polar low developments were captured by dropsonde measurements and LIDAR retrievals. In one case (3-4 March), the full life cycle of a polar low over the Norwegian Sea was captured by three consecutive flights. These measurements represent a unique legacy for polar low research by: a) Mapping the three-dimensional structures of a polar low at three different stages of development; b) Serving as a test-bed for validation of model simulations in an otherwise data-sparse region.

Another polar low that formed in almost the same area over the Norwegian Sea two weeks later (16-17 March) was much more poorly predicted, with many of the operational models at the time placing the polar low several hundred kilometers too far southwest. We will present results addressing possible causes of this difference in predictability.

We will summarize how the campaign data have contributed to new knowledge about polar lows, as well as to new forecasting tools, and we will identify the main remaining challenges.

Welcome!