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Notes From The 2008 AMS Weather Conference

by Matt Zaffino

Bio | Email | Follow: @Zaffino

Posted on June 30, 2008 at 1:31 PM

Updated Wednesday, Nov 4 at 2:47 PM

I'm writing this from the Denver Airport on my way home from the annual American Meteorological Society's Broadcasters Conference. The conference is one way that helps me stay on top of all the advances in the science of weather and climate and the state of the industry of broadcasting. It's cool because it also gives me a chance to re-connect with broadcasters from other cities and share new ideas on how to best communicate with and connect to viewers.
The conference began with a one-day workshop on "dual polarity" Doppler radar. As if Doppler wasn't enough? Dual polarity radar gives information on rain droplet size and shape. It also gives us much better information on rainfall rates and accumulation. This is great for potential flood events, but also for distinguishing precipitation type and the freezing level. Cool huh? I think so. Eventually all the National Weather Service radars and hopefully Doppler 8000 will all be "dual pole" radars. Like all radars, dual polarity radars send out bursts of energy that bounce off targets (precipitation for weather radars) and then interpret the energy that bounces off those targets and returns to the radar. But what the heck is "polarity"? It means that the radar only reads energy oriented in one direction. Think of a doorway that has string of beads hanging in it, such as those that were popular in the 1960s or in some Chinese restaurants. People pass through the beads easily because our bodies are oriented vertically, like the strings of beads. But if you try to pass through the beads holding a broomstick perpendicular to the beads and parallel to the floor, you have a much harder time of it. This is an example of polarization. With dual pole radar, the radar first emits energy polarized vertically, and then emits the next burst with horizontal polarization. This all happens repeatedly and takes only microseconds since the radar energy bursts travel at the speed of light. The different polarities return different information about the targets, and that's how we can tell the difference between rain, snow and hail with dual-polarity radar. It's pretty cool science, and in some ways will be more useful to us in the Northwest than Doppler, which is excellent at showing wind patterns in thunderstorms that can tell us about possible tornadoes and other forms of damaging winds. We don't a lot of severe thunderstorms in the Northwest, but we do have a lot of severe weather related to snow, heavy rain and ice, and dual-polarity radars are great tools in those situations.

Much of the rest of the conference was dedicated to the discussion of climate change. We heard from many climate experts about the latest general circulation models (GCMs) and what they are predicting about the earth's climate and how we humans are impacting it. While there is much debate about how climate change will shake out region-by-region, and how fast world climate is changing, some things are clear.

We are changing the composition of the earth's atmosphere by adding carbon dioxide (CO2) and other gasses, mainly through the burning of fossil fuels. Here's a sobering fact: half of all the CO2 humans have added to the atmosphere since the beginning of the industrial revolution about 150 years ago has been added since 1983. Half. That means human-caused climate change is just now gearing up.

The latest research indicates we're likely to see more extreme precipitation events, and more frequent heat waves and less frequent cold waves. Does this mean it will never be cold again? Of course not. There is still a ton of natural variability in the atmosphere-ocean system. Climate features like our current La Nina will continue to have a major impact on our weather. But all indications are that the overall trend is toward a warmer planet.

There's been criticism lately of Academia by human-caused climate change deniers. Near as I can tell, they seem to think Academia has some hidden agenda for pushing climate change onto the general public. I asked some leading climate researchers at the National Center for Atmospheric Research (NCAR) about this and the response was: "I can always get funding for other types of research." I find it curious that human-caused climate change deniers seem to think that the over 2500 scientific reviewers of the International Panel on Climate Change (IPCC), which includes many of the worlds leading scientists from over 30 countries, are conspiring to pull something over on all of us. In my experience, getting ten meteorologists to agree on a two-day forecast can be difficult. Not that I think skepticism of science is a bad thing. It's a necessary and valuable part of the scientific process. The science put forth by the IPCC is open to anyone who cares to dive into it.

To be sure, there are problems with the 15 major GCMs that are used to forecast world climate. The role of the oceans as a source and sink of heat and CO2 needs to be greatly improved upon. Another weak point in the modeling is cloud physics. With more available water vapor in the atmosphere, how will clouds respond and will there be a net loss or gain of incoming solar radiation? The models also don't take into account the melting of perma-frost. This could be a major player in the release of greenhouse gases to the atmosphere.

Clearly, there is much work to be done to more fully understand and predict global climate. In the face of the potential for a rapidly changing climate, it's important that we all continue to talk about the weather, and try to do something about it.

Matt Zaffino
KGW Chief Meteorologist