Wind field calculation is a common problem in different environmental applications from design of wind farms to forest fire propagation prediction. Calculating the wind field is a complex problem that involves solving huge linear systems. Solving such systems requires the use of iterative methods, such as Preconditioned Conjugate Gradient (PCG) that in most cases take long execution time. The PCG solver with different preconditioners has been analyzed and the performance and scalability of this solver has been determined. The most time consuming operations have been identified and a new method has been developed to improve the parallelization reducing the execution time and increasing the scalability. The new method has been applied on a wind field simulator, called WindNinja, usually coupled to forest fire propagation models. The results are very promising and the new parallelization method appears as a key point to be integrated in other approaches.