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Compliments radar

Min temperature

Anvil growth

Storm top dynamics

Equilibrium temp

Phase change

RFD's

Anvil-induced boundaries

Storm morphology

Future hypotheses

Storm top dynamics and GOES thermal infrared imagery (contd)

Mixing comes into play by creating a temperature gradient between the undiluted ascending updraft and the environment. This phenomenon was first observed by Roach, 1966 as he compared stereoscopic cloud heights with radiometric temperature readings taken by a U2 aircraft. There were 20 to 30 °C warm biases in the radiometric temperatures vs. theoretical parcel temperatures. Roach postulated there must be a zone of mixing at the cloud edge concealing the true parcel core temperatures. The figure below is a schematic of how mixing may create a radiometric warm bias.

Figure adapted from Roach, 1966.

The GOES-8 10.7 µm T_b will be strongly affected by the amount of mixing occuring in the cloud edge. Stronger mixing will make for a warmer T_b all other things being equal. See below for an example.

The amount of mixing will depend on:

• temperature gradient
• wind shear

Here is another cause of a overshooting top warm bias.

• Adler (1982) observed a 3 to 10 ° C warm bias of the GOES 10km IFOV to that of the AVHRR 1km IFOV.
• The current GOES should have a lower warm bias due to better resolution.

Next, looking at the three classes of storm top IR signatures.