9.1. Upperair Station Model#

The upperair station model uses the same basic structure that is done for the surface, including where the mass and temperature fields go and wind speed and direction. However, there are a lot less data taken since we only collect temperature, moisture, and pressure values directly and infer wind speed and direction through GPS location differencing. The basic structure of the upperair station model is given in Figure 9.1 with full descriptions given in the table below the figure.

upperair station model

Fig. 9.1 Graphic representation of the parameters plotted around the upperair station model.#

Parameter Reference

Description

FF

The wind speed. Typically reported in knots, but can be mph or m s-1.

WD

The wind direction. Indicated by the stem, the wind is always described by where the wind is coming from. The depiction above would be a west wind.

TT

The temperature in Celsius (different from the surface model)

DD

The dewpoint depression or spread between the temperature and the dewpoint.

For example at 500 hPa,

DD = T(500) - Td(500)

If the dewpoint is the same as the temperature (i.e., the atmosphere is saturated at 500 hPa), then the dewpoint depression (DD) is zero.

Very Moist Air DD = 0

Very Dry Air DD >= 30

HHH

The height that you must go (referenced to mean sea level) up in order to reach the stated pressure level at the given location. This is in a code. See Table Table 9.1 below for a description of how to interpret at different pressure levels.

To decode the three-digit height values that are plotted on an upperair map you can use your knowledge of common atmospheric conditions at different levels with this handy table to be able to add in the left off values to make the plotted observations more compact. Note how at the highest levels of the troposphere (e.g., 250 and 200 hPa) there are two missing values, one at the beginning and end of the plotted value for the station model.

Table 9.1 Decoding upperair heights#

Pressure (hPa)

Prefix to Plotted Value

Suffix to Plotted Value

Plotted

Height (m)

850

1

–

530

1530

700

2 or 3*

–

180

3180

500

–

0

582

5820

300

–

0

948

9480

250

1

0

028

10280

200

1

0

164

11640

* Use the value that will bring the plotted value closest to 3000 meters.