Dymecs dynamical and microphysical evolution of convective storms nerc standard grant
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University of Reading: Robin Hogan, Bob Plant, Thorwald Stein, Kirsty Hanley, John Nicol Met Office: Humphrey Lean, Carol Halliwell. DYMECS: Dynamical and Microphysical Evolution of Convective Storms (NERC Standard Grant). The DYMECS approach: beyond case studies.

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DYMECS: Dynamical and Microphysical Evolution of Convective Storms (NERC Standard Grant)

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Dymecs dynamical and microphysical evolution of convective storms nerc standard grant

University of Reading: Robin Hogan, Bob Plant, Thorwald Stein, Kirsty Hanley, John Nicol

Met Office: Humphrey Lean, Carol Halliwell

DYMECS: Dynamical and Microphysical Evolution of Convective Storms(NERC Standard Grant)


The dymecs approach beyond case studies

The DYMECS approach: beyond case studies

Track storms in real time and automatically scan Chilbolton radar

Derive properties of hundreds of storms on ~40 days:

  • Vertical velocity

  • 3D structure

  • Rain & hail

  • Ice water content

  • TKE & dissipation rate

NIMROD radar network rainfall

Evaluate these properties in model varying:

  • Resolution

  • Microphysics scheme

  • Sub-grid turbulence parametrization


Dymecs dynamical and microphysical evolution of convective storms nerc standard grant

Nimrod radar

1.5-km model

500-m model

200-m model

Kirsty Hanley


Dymecs dynamical and microphysical evolution of convective storms nerc standard grant

Nimrod radar

1.5-km model

Too few

500-m model

200-m model

Too many

Kirsty Hanley


Storm size distribution

Smagorinsky mixing length plays a key role in determining number of small storms

Storm size distribution

1.5-km model

500-m model

Kirsty Hanley


20 april 2012 25 aug 2012

20 April 201225 Aug 2012

500-m model best

200-m model best

1.5-km model best

200-m model best

Kirsty Hanley


Vertical profile

First 60% of storms by cloud-top height

Next 30%

Top 10%

Observations 1.5-km model 1.5-km + graupel

Vertical profile

Ice density too low?

Higher reflectivity core

Thorwald Stein


Vertical profile1

First 60% of storms by cloud-top height

Next 30%

Top 10%

Observations 200-m model 500-m model

Vertical profile

Thorwald Stein


Estimation of vertical velocities from continuity

Estimation of vertical velocities from continuity

  • Vertical cross-sections (RHIs) are typically made at low elevations (e.g. < 10°)

  • Radial velocities provide accurate estimate of the horizontal winds

  • Assume vertical winds are zero at the surface

  • Working upwards, changes in horizontal winds at a given level increment the vertical wind up to that point

  • Must account for density change with height

Key uncertainty in models is convective updraft intensity and spatial scale

Can we estimate updrafts from Doppler wind sufficiently well to characterize the distribution of intensity and spatial scale?

John Nicol


Dymecs dynamical and microphysical evolution of convective storms nerc standard grant

Estimating retrieval errors from the Unified Model

Vertical wind (m/s)

Reflectivity (dBZ)

Retrieved vertical wind (m/s)

Horizontal wind (m/s)

Retrieval error (m/s)

John Nicol


Dymecs dynamical and microphysical evolution of convective storms nerc standard grant

dBZ

u (m/s)

w (m/s)

12:45 07 August 2011

16:37 07 August 2011

John Nicol


Scientific and modelling questions

Scientific and modelling questions

  • What is magnitude and scale of convective updrafts? How do two observational methods compare to model at various resolutions?

  • What model configurations lead to the best 3D storm structure and evolution, and why?

  • How good are predictions of hail occurrence and turbulence?

  • How is boundary-layer grey zone best treated at high resolution, and what is the role of the Smagorinsky length scale?

  • Does BL scheme “diffuse away” gust fronts necessary to capture triggering of daughter cells and if so how can this be corrected?

  • Can models distinguish single cells, multi-cell storms & squall lines, and the location of daughter cells formed by gust fronts?

  • What are the characteristics common to quasi-stationary storms in the UK from the large DYMECS database?

  • Can we diagnose parameters that should be used in convection schemes from observations?


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