Astroclimatology Forecast Models

Forecasting Cirrus Cloud and Water Vapor

• The Feasibility of Forecasting Cirrus Cloud Cover and Water Vapor above Telescope Sites in Northern Chile PASP 109: 208-214, 1997 February, by A. Erasmus and R. Peterson.

  The method is based on combining satellite current image in the 6.7 and 10.7 microm. channel with wind and temperature profiles forecasted by a prediction center.

  ESO Reports

• Operational Forecasts of Cloud Cover and Water Vapour above Paranal and La Silla Observatories by A. Erasmus and D. Maartens, 15 March 1999, ref:ESO-VPS/97/9480/HWE, (pdf)
• Maintenance, Upgrade and Verification of Operational Forecasts of Cloud Cover and Water Vapour above Paranal and La Silla Observatories by A. Erasmus and D. Maartens, 30 June 2001, ref:ESO-ODG/99/8362/GWI, (pdf)
• An analysis of cloud cover and water vapor for the ALMA project: a comparaison between Chajnantor (Chile), Chalviri (Bolivia) and five sites in Argentina by A. Erasmus, 31 December 2002, ref:ESO-ODG/02/6419/GWI, (pdf)
• A Satellite Survey of Water Vapor and Cloud Cover in Northern Chileq by A. Erasmus and C. van Staden, CTIO 2001 (pdf)
• Maintenance, revision of the movement algorithm and development of a transparency index by A. Erasmus, D. Maartens and R. van Rooyen, 30 April 2003, ref:ESO-ODG/01/8636/CNI, (pdf)
• A Satellite Survey of Cloud Cover and Water Vapour in Morocco and Southern Spain and a Verification Using La Palma Ground-based Observations by A. Erasmus and Ruby van Rooyen, 14 February 2006, ref:ESO-TSD/04/6179/GWI/LET, (pdf)

  ESO related Publications

  A. Erasmus, M. Sarazin; Forecasting Precipitable Water Vapour and Cirrus Cloud Cover for Astronomical Observatories: satellite image processing guided by synoptic model dissemination data; Conf. on Image and Signal Processing for Remote Sensing IV, SPIE 4168, Barcelona, Spain, Sep. 2000.
  A. Erasmus, M. Sarazin; Utilizing Satellite Data for Evaluation and Forecasting Applications at Astronomical Sites; Astronomical Site Evaluation in the Visible and Radio Range, IAU Site 2000, ASP Conference Series Vol. 266, 2002.
  A. Erasmus; An Overview of Recent Site Survey Studies for ELT projects: Aerial survey and site comparisons of cloud cover and water vapor using satellite data; Proc. IAU Symposium nr:IAUS232, 2005.

  PWV Verification

  Measured

  Ground

  Satellite

  Forecast	RMS	MAE	ME	RMS	MAE	ME
  Period 1	0.68	0.53	-0.41	0.71	0.58	-0.46
  Period 2	1.14	0.99	0.29	0.90	0.76	0.12
  Period 3	1.06	0.78	0.31	0.92	0.69	-0.13
  Period 4	0.93	0.82	-0.15	0.48	0.38	-0.06
  Summer Periods	1.11	0.92	0.3	0.91	0.73	0.04
  Winter Periods	0.77	0.63	-0.32	0.63	0.5	-0.31
  All Periods	1.01	0.82	0.08	0.84	0.72	-0.06

  Root mean square error (RMS), mean absolute error (MAE) and mean error (ME - measured minus forecasted) between forecasted and measured (by ground monitor and satellite respectively) PWV (mm) at Paranal using the final version (2.5) of the forecasting programme.

  In addition, a comparison between the Antofagasta Radiosonde, 6.7 µm Satellite and Paranal Ground monitor measurements of precipitable water vapor (PWV) was also conducted. This comparison showed that there is good agreement between these three different measurement methods.

  Examples

  Some synoptic information on water vapor circulation over the southern Pacific can be found on the H2O flow chart, Demo movies of 24-hour forecast message issued on Nov. 29 1993 at 15h UT for subsequent 3-hourly bins (170kB mpeg), 24-hour of input images on June 14-15, 1993 (480kB mpeg), and 2 weeks of input images on June 14-29, 1993 (4mB mpeg).

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Send comments to <Marc.Sarazin@eso.org> Last update: Apr 24, 1997 Back to Astroclimatology homepage.