This paper serves as the introduction to a collaborative experiment (the Program for Intercomparison of Land Surface Parameterization Schemes—PILPS 2(e)— experiment). Twenty-one land surface schemes (LSS) participated in the experiment, which used data from the Torne-Kalix River in northern Scandinavia. Each group ran their computer models under a set of prescribed conditions to assess how well each of the models is able to represent land surface conditions in cold climates. Cold regions have been identified as the most vulnerable to future climate change, but have been largely neglected by hydrologists. As such the paper is particularly important to the land surface modelers, as well as to the global climate community.

The PILPS 2(e) experiment builds on earlier PILPS experiments by creating a multi-year, spatial dataset that allows exploration of the LSS ability to capture key processes spatially in cold regions. In general, the experiment demonstrated that the majority of the LSS are able to capture the limitations imposed on annual latent heat by the small net radiation available in this high latitude environment. Between-model differences in net radiation are governed by the radiative surface temperature in winter months and by differences in surface albedo in spring/early summer.

Climate modeling studies indicate that global warming may be larger at high latitudes than elsewhere, primarily due to reduced albedo associated with reduced sea ice extent and seasonal snow cover. The strength of the coupling between the ocean, land, and atmosphere in the Arctic is particularly important because of its influence on the net transfer of heat northward, and fresh water southward, which in turn affects global climate and weather. All of these considerations motivate us to improve the way high-latitude land surfaces are represented within the coupled land-atmosphere models used to predict future earth climate.

The Project for Intercomparison of Land Surface Parameterization Schemes (PILPS) has been organized under the World Climate Research Programme to coordinate land-surface scheme intercomparisons. The goal is to achieve improvements in land-surface schemes for the benefit of numerical weather prediction and climate models in order to improve confidence in the simulated land-surface quantities. The specific objective of the PILPS 2(e) experiment described here was to evaluate the performance of uncoupled land surface parameterizations in high latitudes.

I was working on my Ph.D. at the University of Washington in Seattle, Washington, with a focus on arctic hydrology and hydrologic modelling. My adviser, Dr. Dennis P. Lettenmaier, the Director of the Surface Water Hydrology Research Group, became involved in the PILPS experiments and asked me to help to coordinate an arctic model intercomparison.