WMO Normals User Guide

Comprehensive user guide for the WMO Normals Explorer, detailing how to navigate the map, filter stations, and visualize climatological data.

Access the Application: Return to Explorer

1. Introduction

The WMO Normals Explorer provides access to the official World Meteorological Organization Climatological Standard Normals for the 1991-2020 reference period. The dashboard allows users to dynamically explore long-term averages for temperature, precipitation, pressure, and sunshine duration across thousands of global stations.

2. Global Navigation (Sidebar)

The sidebar on the left controls the global view of the application and filters the map.

Select Parameter: Choose which climatological variable to display on the map (e.g., Mean Temperature, Precipitation, Sunshine Duration).
Select Time Period: Define whether to show the “Annual” average/total, or the normal for a specific month (e.g., Jan, Feb).
Select Country: Filter the displayed stations by country. Leave as “All Countries” to see global data. By choosing a specific country, the map will automatically zoom to its bounding box.
Select Station: A dropdown populated with stations matching the selected country filter.

Try it out: Explore Bremen Data

To see a great example of European normals: 1. In Select Country, choose Germany. 2. In Select Station, choose BREMEN (WMO ID: 10224). 3. The dashboard will switch to detailed data for Bremen’s 1991-2020 climate.

3. Main Navigation Tabs

The application features two primary navigation views accessible from the top navbar:

Map View

The default view is an interactive WebGL-accelerated map showing all available climate stations matching your filters.

Colored Dots: Stations are colored dynamically based on the Parameter and Time Period chosen in the sidebar (e.g., darker blue for higher precipitation, red for higher temperatures).
Selection: Click any dot to select a station. The station will be highlighted with a red ring, and the app will automatically transition to the Dashboard view.
Layer Control: Use the floating panel on the top-left of the map to switch between OpenFreeMap Positron (light mode), OpenFreeMap Bright (classic), or Sentinel-2 Satellite imagery, and toggle map labels on or off.

Dashboard

The Dashboard displays the detailed climatological normals matrix for a selected station. It activates only after clicking a station map marker or selecting one from the sidebar dropdown.

Dashboard Header

Station Info: Displays the Name, Country, WMO ID, and Elevation of the selected station.
Export CSV: Click the “Export CSV” button to download a spreadsheet containing all calculated 1991-2020 parameters (Annual and Monthly values) for the selected station.

Matrix & Graphs

Visualizations: Below the matrix, the dashboard dynamically generates interactive charts for all available climatological parameters:
- Walter-Lieth Climate Diagram: A specialized bioclimatic chart showing the relationship between temperature and precipitation throughout the year.
  - Red Line: Mean monthly temperature.
  - Blue Line: Monthly precipitation (scaled 1:2 against temperature).
  - Shading: Blue areas indicate humid periods (Precipitation > 2x Temp); yellow/orange areas indicate arid periods.
  - Bars (bottom): Black bars indicate potential frost risk months (Min Temp < 0°C).
- Temperature Curves: Displays seasonal variability with Average Daily Maximum (Dark Red), Mean (Red), and Minimum (Light Red) temperature lines.
- Precipitation: A blue bar chart showing total monthly accumulated rainfall and snowfall in millimeters (mm).
- Precipitation Days (≥ 1mm): Purple bars showing the frequency of significant precipitation events (days per month).
- Sea Level Pressure: A blue line chart showing seasonal variations in mean monthly atmospheric pressure in hectopascals (hPa).
- Vapor Pressure: A green shaded line chart showing absolute humidity trends in hPa.
- Sunshine Duration: Yellow bars showing total monthly sunshine hours.

4. Parameter Definitions

The normals mapped and presented in the dashboard adhere to the following WMO standard definitions:

Parameter Name	Definition	Unit
Mean Temperature	Daily mean temperature averaged over the period	°C
Max Temperature	Daily maximum temperature averaged over the period	°C
Min Temperature	Daily minimum temperature averaged over the period	°C
Precipitation	Average monthly or annual accumulated precipitation	mm
Precipitation Days	Average number of days per month/year with precipitation \(\ge\) 1.0 mm	days
Mean Sea Level Pressure	Average MSLP over the period	hPa
Mean Vapor Pressure	Average vapor pressure over the period	hPa
Sunshine Duration	Average monthly or annual total hours of sunshine	hours

5. Official Source and Methodology

These normals are derived directly from the WMO collection of Climatological Standard Normals for 1991–2020, submitted by National Meteorological and Hydrological Services.

Depending on local operational constraints and data gaps, participating nations use standardized WMO guidance (e.g., WMO Guidelines on the calculation of Climate Normals, WMO-No. 1203) to estimate missing values where appropriate and produce high-quality reference data.

For more details on calculation methods, visit the WMO Community Knowledge Hub.