Radar data from cold air outbreak during Constrain

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Radar data from cold air outbreak during ConstrainKirsty McBeath


• Looking at cases of cold air outbreak in the Northwest approaches• 4 flights during Constrain examined these conditions during January 2010• Radar data from these cases used for comparisons with UKV model•This data is from a case on January 31st 2010 which coincides with flight b507 of the BAe-146 research aircraft

MODIS 31st Jan 2010

Introduction


Overview of observations


Position of radar

300km

300kmDruim-A-Starraig

radar


Data from radarData available every 5 minutes for 24 period

Using data at 15min intervals for 4.5h period to correspond to model

Scans performed at a range of angles: 0.5°, 1.0°, 1.5°, 2.5°

Data up to height of 12km

More observations close to the surface and close to the radar due to beam overlap


Radar Model

Cloud microphysics fields in model used to forward model reflectivity values


Cluster analysis


Radar Model

10dBz threshold used to select regions of precipitation (~4mm/day) in both datasets

Cluster Analysis


Cluster Analysis• Identified cells tracked in time for both datasets

• Cells excluded from dataset if they moved outside the region of interest, or were only seen to decay

• 75 cells identified in observations (+109 excluded cells)

• 42 cells identified in model data (+59 excluded cells)


Cluster size

Both datasets have same mode in size distribution

Model has fewer large cells than radar observations

Much greater spread in sizes seen in radar data


Cell size with time


Maximum size

Model also has much less spread than observations in the maximum cell size reached


Cluster lifetime

Model has more cells with short lifetimes than are seen in the observations


Cluster growth


Cluster Growth Rate

Growth Rate <0.5 >0.5

Radar 40% 29%

Model 53% 32%


Reflectivity with cell lifetime

Model data has higher cell reflectivity values and more variation in cell reflectivity throughout cell lifetime


Cells encountered by the BAe-146

19 cells intercepted by BAe-146 during b507

Mean cell size = 15.7km ( = 9.04km)Mean (full dataset) = 12.06km ( = 7.25km)


Cells encountered by the BAe-146

Cells intercepted by aircraft are slightly larger and longer-lived than average


Next steps

• Repeat this analysis for different model configurations

• Look at impact of using different reflectivity thresholds for cluster analysis

• Examine model data with higher spatial and temporal resolution

• Compare data from radar and model with data from the 146 research aircraft


Questions

Documents

Radar data from cold air outbreak during Constrain