An error has been found in one of the MarkSim data files. Some of the cluster correlation matrices are singular. This has been corrected. To update your installation download the file avmats.cor and replace the existing one in your directory \markdat\. Rest assured that if you haven't noticed MarkSim crash with an error message for an arithmetic exception then you haven't encountered the problem and all your simulations will have been correct. The singular correlation matrices result in MarkSim trying to take a square root of a negative number and the simulation stops. The clusters affected are rare ones and haven't showed up in over 4 years of testing and work with MarkSim.

Have you ever needed daily met data and found that the nearest met station is 25km away and over a range of hills? That the data are recorded on paper and you'll have to transcribe them all? That they are only available for the years 1945 to 1953? You're in good company! Almost anyone trying to run a crop model or evaluate the probability of frost or drought knows the feeling only too well.

Wouldn't it be magic to create a series of 30 years of daily rainfall, maximum and minimum temperatures, and global radiation with the click of a mouse for the very field that you are working in? MarkSim can do that for you.

MarkSim works from a set of interpolated climate surfaces to fit a Markov model to the estimated climate data. It uses a third order model with a special stochastic resampling of the model parameters to realistically simulate the rainfall and temperature variances for almost anywhere in the tropics. To see how it does this, consult the theory section.

MarkSim output is especially tailored for users of the DSSAT suite of crop models. The software comes with a set of background coverages that help you find the place you're looking for. A handy climate display tool allows you to select the exact climate you wish to simulate. Batch facilities allow you to simulate multiple sites in one go.

What does MarkSim look like?

The working screen

This screen shot show the background filled in with the coverages of rivers, roads, towns and contours for easy location. It is zoomed in to show the environs of CIAT, which lies between Cali and Palmira. By merely pointing at this map, the user can identify the point

to simulate, or alternatively view the climate. These backgrounds cover the whole of Latin America and the Caribbean, Africa and South East Asia. A small part of the Middle East is still without cover but this is planned for the next release. The Service Icons are explained in the User Reference Section of the manual.

The Climate Diagram

The climate diagram shows the rainfall, maximum, mean and minimum temperatures. This case is for CIAT. It can display the data in polar or Cartesian coordinates and as shown by calendar month or rotated to eliminate date effects.