Most of the time, we ignore the temperatures recorded in downtown Baltimore. The National Weather Services decided back in 1950 that the thermometer readings they were getting from the instruments on the roof of the Customs House were unreliable, and not representative of the surrounding region. Rooftops are notoriously hot, and the brick and stone buildings, concrete sidewalks, asphalt roofs and streets, smokestacks and air conditioning exhaust all make cities hotter than their surrounding suburbs and countryside, especially at night.

So, in 1950, the weather service moved Baltimore's station of record out of the city, and established Friendship Airport - now BWI Marshall - as the spot where official "Baltimore" weather data has ever since been gathered.

In April 1998, the weather service decided that the roof of the Customs House was not even a good place to record urban temperatures. So, they built a new station beside the Maryland Science Center, and discontinued data collecting at the Customs House after nearly a century of continuous record-keeping.

Unfortunately, it wasn't an ideal choice. The spot is often sheltered from the wind by the Science Center itself. And, because the site isn't a priority station for the weather service, breakdowns aren't fixed quickly, and large data gaps crop up. The station does not report wind, visibility, and sky condition. Only temperature, dew point, precipitation and barometric pressure are reported. Temperatures there are usually warmer than at BWI, reflecting a continuing heat island effect. We've seen it again this week, with Inner Harbor highs breaking 100 degrees on Tuesday and Wednesday, while BWI highs lagged by a degree or two. But I digress.

Climate scientists have done quite a bit of research on the impact of urban development on the micro-climate of a big city. For example, they've established that cities affect the weather. The extra heat rising from a city creates updrafts and convection that lift warm, moist air high into the atmosphere. There, it cools, the moisture condenses out as rain, and regions downwind of the city actually get increased rainfall.

This heat island effect also increases the misery and cooling costs of city residents, and that has prompted research into how the effect might be dampened by planting roof gardens, resurfacing rooftops in white instead of black, and simply planting more trees in our cities.

All of this brings me to a point where I can provide a link to an interesting discussion of some recent NASA-funded research into the issue. Here's the link. Be sure to follow the blue links at the bottom of each page. There's lots to read here.