Interpreting Temp profile luchtvaartmeteo.nl

Introduction
The Temp Profile is the result of measurements taken by a radiosonde under a weather balloon.

Notation
Colors:

• the red line indicates temperature
• the blue line indicates dew point temperature
• the bold green diagonal denotes the 0 degrees Celsius isotherm
• the black lines (isohumes) indicate the maximum amount of water vapour that could be held in the atmosphere (saturation mixing ratio) for each combination of temperature and pressure
• the yellow line denotes the dry adiabate according to Gold (max) temp
• the vertical orange lines indicate the moist adiabates

The distance between the red and the blue line denotes the humidity at the pressure level indicated along the vertical axis. If the red and blue line coincide, the humidity is 100% and the presence of clouds is very likely. If the temperature is between 0 and -10 Celsius in layered clouds, or 0 and -15 Celsius in active frontal clouds, icing is to be expected if the red and blue line are close together. In Cb’s the temperature range for ice is 0 to -23 Celsius. Always check for warnings in valid LLFC or SIGWX charts. Experts use Temp profiles for analyses of stability and (conditional) instability of the atmosphere.

By knowing the (forecast) temperature at a particular time one can deduct when and how thermals will develop. The cloud base and thickness of clouds depend – apart from the temperature and dew point temperature profiles – on the actual temperature on the ground.

The cloud base (in dry conditions not visible) can be deducted by starting at the actual ground temperature and then by following the dry adiabate until this adiabate intersects the temperature profile. At this point the rising air is no longer warmer than the surrounding air.

The thickness of clouds can then be deducted by starting at the dew point temperature on ground level and then by following the isohume intersecting this point until the isohume intersects the temperature profile.

The amount of stability or instability can be deducted by comparing the lapse rate of the temperature profile with the lapse rate of the dry and moist adiabates. The smaller the lapse rate the more unstable the air, and the higher the lapse rate the more stable the air. When the temperature profile follows an isotherm (parallel to the green isotherm line) the air is completely stable.

The amount of stability or instability, the moisture of the air together with the actual temperature on the ground can give an idea if or when significant weather (TS, CB) may occur.

The values of the following derived parameters are available:

• ELEV: Elevation
• PLCL: Lifting Condensation Level (pressure)
• TLCL: Temperature Lifting Condensation Level
• PCCL: Convective Condensation Level (pressure)
• TCCL: Temperature Convective Condensation Level
• PLFC: Level of Free Convection (pressure)
• TLFC: Temperature Level of Free Convection
• GLFC: Gold Level of Free Convection
• PELB: Equilibrium Level (pressure)
• TELB: Temperature Equilibrium Level
• GELB: Gold Equilibrium Level
• PFRZ: Freezing Level
• TROPO: Tropopause Height
• MAXWND: Maximum Wind
• K: K_index
• LIFTED: Lifted index
• SWEAT: Severe weather (Sweat) index
• TOTALS: Totals index
• BOYDEN: Boyden index
• BRADBURY: Bradbury index
• RACKLIFF: Rackliff index