arctic cyclones

Rationale behind the "Arctic cyclones" work package

There is a strong need for improvement in the observations and modeling of the Arctic atmosphere. Current climate models, global as well as regional, are more unreliable in the Arctic than for most other regions. This is demonstrated both by the apparent difficulty in

describing current Arctic climate with these models, and by the inter-model spread in scenarios for future climate, which is larger in the Arctic than elsewhere. There are many reasons for this. Some stem from the inability of models to handle mesoscale synoptic disturbances (even the present-day observational network is incapable of detecting all mesoscale cyclones). Some of the model problems are related to an insufficient understanding of several important local feedback mechanisms that appear to be special to the Arctic. Many of these processes are sub-grid scale in climate models and need to be parameterized.

Developing such descriptions has an unavoidable empirical component, and part of the problem in the Arctic is a lack of process-scale data. Many of these processes deal directly with the energy transfer at the surface, and are therefore directly relevant for the melting of the sea ice. To understand these processes, we follow the DAMOCLES objectives to increase the observational coverage of the Arctic marine atmosphere and to improve its modeling. To achieve this overall objective, a focus on the following processes is needed:

  • Dynamics and occurrence of mesoscale cyclones. Mesoscale cyclones, such as Polar lows, are common particularly in the marginal ice zone. The strong winds associated with the cyclones have a major influence on sea ice dynamics, and present a serious risk for navigation. In addition, mesoscale cyclones are supposed to make a large, but insufficiently known, contribution to the lateral transport of heat and moisture into the Arctic atmosphere.
  • …..

 Arctic cyclones

-          A grid of complex-instrumented ice-tethered buoys based on new technology (link to core theme 1 and 3) and a grid of simple-instrumented ice buoys embedded within that grid will be installed over the Arctic Ocean for better cyclone detection and analyses.

-          Satellite observations of the following quantities will be made both over sea ice and the open ocean: cloud liquid water path, total water vapour, as well as surface and air temperature. Various data (SSM/I, AMSU, AMSR, and SSM/IS) and new inversion techniques will be applied, and the existing processing algorithms will be improved. The new sensors SSM/IS and AMSR-E will allow an integrated retrieval of both surface and atmospheric parameters and thus also provide potential for the detection of cyclones.

-          The quality of liquid water path and precipitable water path retrievals will be assessed, as well as the systematic weaknesses of NWP models in temperature and moisture in the Arctic.

-          The Arctic cyclone activity will be analyzed on the basis of existing as well as new in-situ data (buoy grid, a Swedish ice-breaker, Polarstern, Russian drift stations) and remote sensing data.

-          The contribution of the cyclones to the transport of heat and moisture over the Arctic sea ice will be analyzed on the basis of operational model fields, which are produced in WP4 utilizing the new in-situ data and remote sensing products in data assimilation.

-          The interaction of atmosphere and sea ice during strong winds and severe storms will be studied on the basis of meteorological and ice drift data from the new buoy array as well as coupled mesoscale modeling. This will be done in co-operation with WP1, and the specific contribution of WP2 is to validate and improve the atmospheric forcing on sea ice drift.

-          The effect of cyclones and local weather conditions on the Atlantic water transport and the West Spitsbergen Current variability will be analyzed (in co-operation with WP3).

As a result of this work, improvements are expected in the detection and statistical description of (a) the Arctic cyclones, (b) their contribution to the transport of heat and moisture, and (c) their effect on sea ice dynamics (applicable in core themes 1 and 4). The result of interpretation of microwave satellite data and atmospheric model data will be supplied to the data assimilation core theme 4. Improvements in NWP and coupled air-ice-ocean modeling will be assessed on the basis of new buoy and satellite data.

Recommendation will be given on future regular deployments of grids of ice buoys operated, e.g., by pan-Arctic weather services (applicable in the overarching activity 3 on short timescales).

Contact person at DTU: Leif Toudal Pedersen