A Vaisala CL31 ceilometer provides cloud base heights (up to 3) and backscattered intensities at 10-meter vertical resolution over a nominal 0-7.5 km altitude range. The data time resolution is 15 seconds. The laser is an InGasAs diode emitting at a wavelength of 910 nm. The ceilometer has been operating continuouly since December 22, 2011.