Differences over small regions!

In this study, we divided Chesapeake Bay into a North and South region.

The Chesapeake Bay is big, but geographically, it’s not that big!

The regions defined by the National Climate Assessment.

The regions defined by the National Climate Assessment.

Let me explain. Many climate assessments for the United States break the country off into regions. For example, in the National Climate Assessment, the Northeast region spans from Maine to Maryland and Southeast covers Virginia to Florida and includes Puerto Rico. So that means someone living in Washington D.C. would have a different climate region than something living nearby in Arlington, VA.

One reason for dividing the U.S. into regions is that weather does not change too much in nearby locations. Yes, it may vary by a degree or two, but for the most part, the daily high for Dover, DE is similar to the daily high of Annapolis, MD. Additionally, many models have coarse grids which cover many different cities and in some cases states. In our study, a single grid cell of the HadEX2 covered part most of coastal Maryland and Virginia.

However, even though the Chesapeake Bay is only a small part of the East Coast, it is at a divide between the Northeast and Southeast climate regions. So it is possible to have different extreme climate patterns in just this small area.

That was our motivation for looking at South and North Chesapeake differently!

Plot of the Week

The Summer Days index is the annual count of days when the highest daily temperature is above 25°C (77°F). In a future post, you’ll hear about what the Summer Days index might be able to tell us about the presence of Vibrio in the future. (Teaser alert!)

Picture3As you can see from the POTM, there have been different Summer Days historical patterns between the North and South Chesapeake regions. In the South Chesapeake, Summer Days have increased by 3.6 days per decade…that’s 36 more summer-like days over the last century!

On the flip slide, North Chesapeake saw a decrease in Summer Days by about -2 days per decade (although this is a weak trend). For another complication, that gridded HadEX2 product saw no historical change!

This demonstrates why apportioning the Chesapeake Bay as North and South makes sense…there are differences in climate extremes even over this small region! Moving into the future, this region is expected to see an increase in Summer Days (3 to 7 days per decade), so it appears the non-trend and slight decrease seen by the HadEX2 and North Chesapeake are a thing of the past.

(and there were a few more indices that had big differences between North and South…but that is for another day!)


Kari Pohl

About Kari Pohl

I am a post-doctoral researcher at NOAA and the University of Maryland (Center for Environmental Science at Horn Point Laboratory). My work investigates how climate variability and extremes affect the diverse ecosystems in Chesapeake Bay. I received a Ph.D. in oceanography from the University of Rhode Island (2014) and received a B.S. in Environmental Science and a B.A. in Chemistry from Roger Williams University (2009). When I am not busy being a scientist, my hobbies include running, watching (and often yelling at) the Boston Bruins, and taking photos of my cat.
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