1. INTRODUCTION

1.1 Background

This document provides guidance for the collection and processing of meteorological data for general use in air quality modeling applications. Such applications include those required in support of air quality regulations as specified in the Guideline on Air Quality Models. Guidance which specifically relates to a regulatory application is so indicated; in addition, recommendations affecting regulatory modeling applications are summarized at the end of individual sections.

Guidance is provided for the in situ monitoring of primary meteorological variables (wind direction, wind speed, temperature, humidity, pressure, and radiation) for remote sensing of winds, temperature, and humidity, and for processing of derived meteorological variables such as stability, mixing height, and turbulence. Most of the guidance is generic in that it supports most categories of air quality models including: steady-state, non-steady-state, Gaussian, and non-Gaussian models. However, material in some sections is probably more useful in support of some types of models than others. For example, the primary focus of the guidance on site selection (Section 3) is the collection of data at single locations for support of steady-state modeling applications. Non-steady-state modeling applications generally require gridded meteorological data using measurements at multiple sites. Support for such applications is provided to the extent that this guidance may be used for selecting sites to monitor the significant meteorological regimes that may need to be represented in these applications. Site selection criteria in these cases must be evaluated in concert with the objectives of the overall network; this falls in the category of network design and is beyond the scope of this document. Similarity, though generically useful, the guidance on upper-air meteorological monitoring (Section 9) is perhaps most useful in support of applications employing gridded meteorological data bases.

One of the most important decisions in preparing for an air quality modeling analysis involves the selection of the meteorological data base; this is the case whether one is selecting a site for monitoring, or selecting an existing data base. These decisions almost always lead to similar questions: “Is the site (are the data) representative?” This question is addressed in Section 3.1.

Minimal guidance is provided on the use of airport data; e.g., for use in filling gaps insite-specific data bases (Section 6.8). For practical purposes, because airport data were readily available, most regulatory modeling was initially performed using these data; however, one should be aware that airport data, in general, do not meet this guidance. The significant deviations to this guidance are discussed in Section 6.7.

The following documents provide necessary background and documentation for this guidance and are incorporated by reference: "Guideline on Air Quality Models" as published in Appendix W to 40 CFR Part 51 [1]; "Quality Assurance Handbook for Air Pollution Measurement Systems: Volume IV. Meteorological Measurements" [2]; "On-site.1-2 Meteorological Instrumentation Requirements to Characterize Diffusion from Point Sources" [3], "Standard for Determining Meteorological Information at Nuclear Power Sites" [4].

1. INTRODUCTION
 1.1 Background
 1.2 Organization of Document