Getting the monthly aggregate precipitation values from ERA5-Land Monthly Averaged – ECMWF Climate Reanalysis

Digging into Climate Data: Getting Real with ERA5-Land Precipitation

Okay, so you’re trying to get a handle on rainfall patterns, maybe for research, policy, or just plain curiosity? You’ve probably heard of ERA5-Land, that treasure trove of climate data from the folks at the European Centre for Medium-Range Weather Forecasts (ECMWF). It’s seriously powerful stuff, but let’s be honest, wading through climate datasets can feel like trying to understand a foreign language. Don’t sweat it! I’m here to break it down and show you how to snag that monthly precipitation data you need.

ERA5-Land: What’s the Big Deal?

Think of ERA5-Land as a super-detailed historical weather record. It’s not just sitting back and watching what happened; it’s actively piecing together observations with fancy computer models to give us a complete picture of past climate conditions. What makes ERA5-Land extra cool is its high resolution – we’re talking roughly 9 km. That’s way sharper than the regular ERA5, which is more like 31 km. Why does this matter? Well, if you’re trying to predict floods or droughts, that extra detail makes a huge difference. Plus, it goes way back, all the way to January 1950, and gets updated practically in real-time. Pretty neat, huh?

Cracking Open the Data Vault: Accessing ERA5-Land

Alright, time to get our hands dirty. The main place to grab ERA5-Land data is the Copernicus Climate Data Store (CDS). Here’s the lowdown:

Decoding the Rainfall: Understanding the Data

So, what exactly is “Total precipitation” in ERA5-Land? Simply put, it’s the total amount of rain and snow that hits the ground. It includes both the big, widespread rain from weather systems and the smaller, more intense showers from thunderstorms. Just keep in mind it doesn’t count fog, dew, or any rain that evaporates before reaching the surface.

The data is given in meters (m) of water equivalent. Basically, imagine spreading all that rain evenly over the area – the “depth” of that water is what the data tells you.

Crunching the Numbers: Calculating Monthly Totals

Now, this is where it can get a little tricky. Depending on the specific dataset you’re using, you might need to do a little math to get the total monthly precipitation. If you’re working with monthly means of daily means, the units will be “m of water equivalent per day.” So, to get the total for the month, you’ll need to multiply by the number of days in that month. And if you want to convert to millimeters (mm), just multiply by 1000.

Example:

Let’s say the monthly averaged total precipitation for January is 0.0004 m/day. January has 31 days, so:

That means you got 12.4 mm of rain that January. Easy peasy!

A Few Words of Caution

• Take it with a Grain of Salt: ERA5-Land is fantastic, but it’s not perfect. Studies have shown it can sometimes overestimate rainfall, especially in the mountains. Keep that in mind when you’re analyzing the data.
• Grid Boxes vs. Reality: Remember, ERA5-Land gives you averages over a grid box, while rain gauges on the ground measure rainfall at a single point. This can lead to differences, so don’t expect the data to perfectly match what you see in your backyard.
• Read the Fine Print: Always check the ERA5-Land documentation for any known issues or quirks in the data. It’s better to be safe than sorry!

The Bottom Line

ERA5-Land is an incredible resource for anyone interested in climate and precipitation. With a little know-how, you can unlock a wealth of information and gain valuable insights into our changing world. So, dive in, explore the data, and see what you can discover! Just remember to be mindful of the data’s limitations, and you’ll be well on your way to becoming a climate data pro.