Tied PhD studentship “Modelling the atmospheric boundary layer of the high Arctic”

Supervisors – Prof Ian Renfrew (UEA), Dr Roland von Glasow(UEA) ,

 Dr John King (BAS), Dr Ian Brooks (Leeds)

                The climate of the Arctic is changing more rapidly than anywhere else on the planet. However our ability to simulate and predict Arctic weather and climate also has greater uncertainties than almost anywhere else. One of the most significant problems that numerical weather prediction and climate models have in the Arctic is in their representation of low-level clouds and the atmospheric boundary layer (ABL) within which they reside. This PhD project will examine ways of improving the representation and prediction of the ABL within numerical weather prediction (NWP) and climate models.   

Boundary-layer schemes in NWP and climate models often perform rather poorly in the high latitudes (e.g. Tjernström et al. 2005, 2008; Birch et al. 2009; Renfrew et al. 2009). The predominance of low-level cloud, weakly and strongly stratified boundary layers and high humidities presents a serious challenge to current models. A new boundary-layer scheme has recently been developed by Mauritsen et al. (2007) that uses a total Turbulent Energy Mass Flux closure. This scheme has recently been implemented in the WRF model (www.wrf-model.org). In this project the impact of this promising new BL scheme will be evaluated for the Arctic through a series of case studies, as well as a longer evaluation period, using the WRF model. The case studies will be drawn from past and upcoming field campaigns.

This is a directly funded project studentship, funded by NERC via the ACCACIA (Aerosol-Cloud Coupling and Climate Interactions in the Arctic) project. It is anticipated that the student will take part in one of the ACCACIA field campaigns, based out of Svalbard in the Arctic, and work closely with the whole ACCACIA project team.

Further Reading:

Anderson, PS And W.D. Neff, 2008: Boundary layer physics over snow and ice, Atmos. Chem. Phys., 8, 3563–3582.

Birch, C., I Brooks, M. Tjernström, S. Milton, P. Earnshaw, S. Söderberg, P.O.G. Persson, 2009: The performance of a global and mesoscale model over the central Arctic Ocean during the summer melt season, J. Geophys. Res., 114, D13104.

Mauritsen, T., G. Svensson, S. Zilitinkevich, I. Esau, L. Enger and B. Grisogono, 2007. A total turbulent energy closure model for neutrally and stably stratified atmospheric boundary layers. J. Atmos. Sci., 64, 4113-4126.

Renfrew, I.A. et al., 2009: A comparison of aircraft-based surface-layer observations over Denmark Strait and the Irminger Sea with meteorological analyses and QuikSCAT winds, QJRMS, 135, 2046-2066.

Tjernström, M., et al., 2005: Modelling the Arctic boundary layer: An evaluation of six ARCMIP regional-scale models using data from the SHEBA project. Bound.-Layer Meteorol. 117, 337-381.

Tjernström, M., J. Sedlar, and M. D. Shupe, 2008: How well do regional climate models reproduce radiation and clouds in the Arctic? J. Appl. Met. Clim. 47.

Further details

Boundary-layer schemes in NWP and climate models can often perform rather poorly in the high latitudes and furthermore a historic lack of high quality observations has meant less work on appropriate parameterization development. A new boundary-layer scheme has recently been developed by Mauritsen et al. (2007) that uses a total Turbulent Energy Mass Flux (TEMF) closure approach, i.e. it incorporates a turbulent potential energy component as well as the standard turbulent kinetic energy component generally used for ABL closure schemes. Theoretically this scheme should be more appropriate for Stable BLs and preliminary evaluations have had some success (Mauritsen et al. 2007). Leading to the scheme being implemented in the WRF model (Angevine and Mauritsen 2010), where preliminary evaluations for a California domain show promise. A comprehensive evaluation of its performance has not been carried out.

In this PhD project the impact of this promising new ABL scheme will be evaluated for the Arctic through a series of case studies using the WRF model. The case studies will be drawn from the ACCACIA field campaigns, where we will have aircraft-based observations for validation, and also from the recent ASCOS (Arctic Summer Cloud Ocean Study) field campaign in which the team were involved. It is anticipated that some further parameterization testing and tuning will be required for accurate simulations. This will be done in collaboration with Project Partners Thorsten Mauritsen (Max Planck Institute for Meteorology, Hamburg, Germany)  and Wayne Angevine (NOAA, Boulder, Colorado).

In addition to the case study evaluation, a more comprehensive evaluation of the TEMF scheme will be undertaken using WRF for the entire field campaign periods (both ACCACIA and ASCOS).

The studentship project fits naturally into Workpackage 4 of the main ACCACIA project: Cloud and Boundary-layer dynamics and modelling. WP4 contains an evaluation of the Met Office's global operational model for the ACCACIA field campaign periods, focussed on the boundary layer, surface exchange and low-level clouds. This will obviously lead to an investigation of the performance of the MetUM's BL scheme and an inter-comparison against this promising alternative scheme based on total turbulent energy closure will be extremely useful and perhaps guide future model development for the MetUM.

The use of the WRF (Weather Research and Forecasting) model is a pragmatic choice as the TEMF scheme is already implemented in this model (Angevine and Mauritsen 2010). There are already a number of model parameterization schemes and settings in WRF that are suitable for polar conditions, and this Polar WRF configuration (e.g. Hines and Bromwich 2008) will be used as far as is possible. The WRF model is already installed on HPC facilities at UEA and is used by several groups here. It has a reputation as being relatively easy to use, and a good choice for PhD projects. It is supported by NCAS computing support.

This PhD project will be supervised by Prof. Ian Renfrew (UEA) with co-supervison from Dr Roland von Glasow (UEA), Dr John King (BAS) and Dr Ian Brooks (Leeds). The student will also work closely with the whole ACCACIA project team (Universities of Leeds, Manchester, York, East Anglia and the Met Office). It is anticipated that the student will take part in one of the ACCACIA aircraft-based field campaigns which are scheduled for spring and summer 2013.

Angevine, W. M. and T. Mauritsen, 2010: The Total Energy - Mass Flux PBL scheme in WRF: Experience in real-time forecasts for California, 19th Symposium on Boundary Layers and Turbulence, American Met. Soc.  

Hines, K.M., and D. H. Bromwich, 2008: Development and Testing of Polar Weather Research and Forecasting (WRF) Model. Part I: Greenland Ice Sheet Meteorology, Mon. Wea. Rev., 136,  1971-1989.