Vaisala Energy Support
Which weather data source should I pick?
Starting in May of 2022, Vaisala now offers our users a choice of weather data from either MERRA2, which is made by NASA, and ERA5 which is made by ECMWF.
The MERRA2 weather data source is what Vaisala has been using previously. Requesting MERRA2 as the weather source will keep your data files and data sources entirely consistent with what you have downloaded from us previously. The weather data that we provide with MERRA2 is
- wind speed
- wind direction
- air temperature
- air pressure
- total precipitable water vapor
The ERA5 weather data source is a new offering that we are excited to be providing our customers. When you select ERA5, you will receive more weather information. The weather data that we provide with ERA5 is
- wind speed
- wind direction
- air temperature
- air pressure
- total precipitable water vapor
- albedo
- total precipitation
- snowfall (precipitation as snow), as water equivalent (see note below)
- snow depth on the ground, as water equivalent
ERA5 Precipitation and Snow
Occasionally, the hourly values for precipitation as snow exceed the total precipitation in the same period by a small amount. This is expected and is an artifact of how the data is stored and transmitted from the source (ECMWF).
To reduce storage and bandwidth requirements, the source data is packed into GRIB messages in a way that introduces a small error. Total Precipitation and Snow are each stored independently from each other and have different packing errors. ECMWF has a good explanation of how they do GRIB packing for weather data here.
More Solar Online Tools Questions
- How accurate is the data in the Solar Time Series Tools?
- The datasets give different answers. Which one is right?
- Why are there so many (5) different versions of solar data?
- Why do the values in my TMY file change?
- What updates were applied to the datasets in November 2019?
- What's the latest month available in the solar time series tool?
- What solar values are shown on the map in solar prospecting and solar time series tool?
- How do I enter a location?
- Why does the map disappear?
- How do I interpret the graphs provided by the Monthly Mean Irradiance Tools in the Prospecting Tools?
- What do the Annual Mean Irradiance Tools in the Prospecting Tools provide?
- How can I compare sites side-by-side in the Prospecting Tools?
- How much area is covered by the Solar Prospecting Tools?
- How accurate are the Solar Prospecting Tools?
- What data is shown in the Solar Time Series Viewer?
- What data can I get from the Solar Time Series Download tool?
- What is the Vaisala 1.0 dataset?
- What is the Vaisala 1.1 dataset?
- What is the Vaisala 1.2 dataset?
- What is the Vaisala 2.0 dataset?
- What is the Vaisala 2.1 dataset?
- What are the units of irradiance?
- What is the “TMY” Data Type in the Solar Time Series Download tool?
- What is the “Long-Term” Data Type in the Solar Time Series Download tool?
- Why does the data not match my observations?
- How do I input CSV files into PVSyst?
- How can I input time series data into PVSyst?
- What is Global Horizontal Irradiance?
- What is Direct Normal Irradiance?
- What is Diffuse Horizontal Irradiance?
- What affects solar radiation at a given site?
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