Antarctic Mesocyclones and Ross Sea Regional Climate Variability

Antarctic Mesocyclones and Ross Sea Regional Climate Variability

Marwan Katurji1 Peyman Zawar‐Reza1, Tony Dale2

1 Center for Atmospheric Research, University of Canterbury

2 University of Canterbury High Performance Compu=ng Centre

www.landcareresearch.co.nz/science/soils-and-landscapes/terrestrial-data-analysis-ross-sea-region

Marwan Katurji ([email protected]) - June, 2015 Antarctic Science Conference, Antarctica - A Changing Environment Christchurch, New Zealand

Presentation structure

The potential of Antarctic Mesocylones (AMC) in controlling regional climate variability within the Ross Sea Region embayment

What is a mesocyclone and what controls it?

How to study AMC, the tool

Example of a regional climate simulation for an AMC

Example of a regional climate simulation for a severe weather AMC

The role of sea ice in AMC potential


Atmospheric Scale Connectivity

From the Comet program


Rotation in the atmosphere - Vorticity

From earth.nullschool.net

From a barista online


Siple Coast Mesocyclone, 24 August 2013

Courtesy of: Andrew B. Archer Antarctic Support Contract - USAP

Sipl

e Co

ast


What is an Antarctic MesoCyclone (AMC)?

Rotational features given various names in the literature

Polar lows Instability lows

Polar air depressions Mesocyclones

Mesoscale cyclone Mesoscale vortex

Polar air stream cyclones

Clockwise rotating bodies of air

Extend from the surface up to ~ 1 km AGL Have surface winds in excess of 15 ms-1 or 54 kmh-1

Have diameters between 100 and 1000 km Exist for average periods between 6 and 24 hours

AMC have the following properties in common


What is an Antarctic MesoCyclone (AMC)?

AMCs have higher latitude cousins called Mesoscale Convective Systems (MCS) or Mesoscale Convective Complex (MCC). MCS or MCC have instabilities arising primarily from solar heating of the land surface, whereas for AMCs it results from the strong vertical gradient of temperature as cold, dry air moves over a warmer sea surface.

Carrasco and Bromwich (1993)


AMC distribution

Carrasco et al. (2003), Parish and Bromwich (1986)


Regional Climate Modeling Process

Governing equations

Numerical methods

Parameterizations Domain

Initial and boundary conditions

Within the Regional Climate Model (RCM) Defined by the user

or from Earth System Models

(current or IPCC projections)

•  RegCM version 4.4.5 (www.gforge.ictp.it/gf/project/regcm/frs/)

•  Developed at the Earth system Physics section of ICTP

•  Dynamical downscaling (enhancing resolution=better resolving processes) of global climate models

•  Can be tuned to specific regions/geographies with user

control of physical schemes


Regional Climate Modeling Process Surface Model Elevation (m)

x-coordinate in Cartesian system (m)

y-co

ordi

nate

in C

arte

sian

syst

em (m

)

ICTP Regional Climatic model V4Range of Surface Model Elevation: 0 to 3768.04 mRange of x-coordinate in Cartesian system: -9.9e+06 to 9.9e+06 mRange of y-coordinate in Cartesian system: -9.9e+06 to 9.9e+06 mFrame 178 in File Anta_50km_SRF.1990010100.nc

mar

wan

Fri M

ay 8

16:

32:4

2 20

15

Surface temperature Air temperature @ 5km AGL

Irradiance Net solar radiation Surface and topography


Terra Nova mesocyclone activity – A modeled case in January 2014

Negative MSLP spatial anomaly

Terra Nova Bay



Dry-cold katabatic outflow colliding with warm moist northerly winds

Precipitation

Wind Vectors



Dry-cold katabatic outflow colliding with warm moist northerly winds

Wind Vectors

Precipitation


Antarctic severe wind event, 15 May 2004

Powers (2006)

Actual event record Extreme winds, sustained 44ms-1 (158 kmh-1), gusts >187 kmh-1

Torn roofs, blown doors in Mc Murdo town Condition 1 declared

Steinholf et al. (2008)

RegCM: Negative MSLP spatial anomaly


Antarctic severe wind event, 15 May 2004 Negative MSLP spatial anomaly

Air temperature 2m AGL

Wind speed 10m AGL

L

L


Sea Ice and low pressure systems tracks

Driving question: How sensitive is the mode-resolved low pressure systems to sea-ice extent?

Tools: Regional climate experimental simulations and a low pressure tracking algorithm.

*

*

Sea ice extent Aug. 01, 2014 Sea ice extent Aug. 31, 2014

Low pressure centers (with sea ice)

Low pressure centers (no sea ice)


Conclusions 1)  AMC are complex meteorological features driven by surface heterogeneity

(sea ice coverage), topography (enhancing vorticity), and synoptic weather systems

2)  AMC have been studied as singular and localized events, but they can influence the Ross Sea regional wind, temperature and precipitation variations over the longer term

3)  It is extremely critical to represent sea ice extent as accurate as possible in both global and regional scale models as they will influence the tracks and intensities of AMC.

4)  It was previously found that AMC could explain up to 46% of the precipitation in the McMurdo Sound and up to 30% over the Ross Ice shelf (Rockey and Braaten, 1995). This phenomena needs further investigation.

The understanding of AMC and their sensitivity to various forcing through regional climate modeling will aid in a better representation of

future climate projections.

Antarctic Mesocyclones and Ross Sea Regional Climate Variability

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