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May 2011

World Cities Plotted by Climatological Normals, May

cities plotted by sunshine, temperature, and rainfall

Last week I created a bubble chart showing seventeen world cities where warm-season (C4) grasses are usually grown. The cities were plotted by average annual temperature on the x-axis, annual sunshine hours on the y-axis, and the size of each city's "bubble" on the chart was proportional to the city's average annual rainfall.

I have now made additional charts, with the number of cities in the dataset expanded to 46 to give a broader picture of the variability in climatological normals. And I have plotted the data on a month-by-month basis for a more detailed look at how the temperature, sunshine, and rainfall vary throughout the year.


Click the image above to view the bubble chart at a larger size. All data used to generate these plots are from the climatological normal tables for world cities as posted on the Hong Kong Observatory website. The bubble charts were created using the ggplot2 package in R.

I find it interesting to see how the average weather data for different cities change throughout the year. Of the 46 cities plotted here, Hong Kong stands out as having relatively little sunshine (on average) in the month of May. And in cities such as Tokyo and Osaka and Shanghai, where warm-season grasses are almost always used on fairways, the golfing season is well-underway but the temperatures are still too low for the optimum growth of warm-season grasses.

I think there is a lot of information in these plots that turfgrass managers may find interesting. As an example, Miami and Hong Kong have nearly the same average temperature in May, but Miami has more than twice the sunshine hours. This is the season when intensive cultural practices are done to control organic matter in bermudagrass greens in Florida; from looking at the bubble chart above it is obvious that the recuperative ability of bermudagrass at Hong Kong is probably much less in an average May than it would be at Florida. 

At which month is the temperature and sunshine at Tokyo the same as Singapore? How does this bubble chart change during the monsoon season in India? And does the sunshine at Hong Kong ever rise to the level of Miami? I'll post a new chart each month to show how the average weather changes in these cities over the course of a year.

New Calendar Page on ATC Website

I've added a new page to the Asian Turfgrass Center website with a calendar of selected turfgrass conferences and educational seminars that may be of interest to turfgrass managers in Asia. This is not a comprehensive list of events, but I will keep it updated with events as I become aware of them. If you would like me to add an event to this calendar, please send me an e-mail with details of the event.


A Plot of Cities Where Warm-season Grasses Grow, and more

cities plotted by sunshine, temperature, and rainfall

I made the bubble plot above to see how the differences in temperature and sunlight and rainfall between cities would appear if plotted this way. The data are from climatological normals provided by national meteorological services and the World Meteorological Organization, collected in some cases from the climate section of a city's page on Wikipedia.

I made this plot for a few reasons. I saw a job posting for a superintendent position in Asia saying that experience working in a Florida-type climate would be desired, and I wanted to plot a few cities this way to see how cities in Asia compared with Florida. Someone also asked me if I thought it was more difficult to manage warm-season grasses in Singapore or in Florida, and I thought that a plot such as this might make my answer more clear. And I also notice as I travel that a grass that grows so well in Honolulu, for example, may not grow well at all in Bangkok. There are clear differences in suitability of grasses for different growing environments. And as I work with some new software, I saw a tutorial to make this type of bubble plot on the FlowingData website and I wanted to try it for myself.

City_by_sun_edit-1 When plotted this way with mean annual temperature on one axis and hours of sunshine on another axis (the area of the circle for each city is proportional to annual rainfall), one can see that the cities in Asia tend to have a higher annual temperature, have less annual sunshine than the cities plotted from the USA, and have substantially more precipitation. A quick look at the bubble plot shows that Singapore, for example, has about 60% the sunshine of Miami while receiving almost twice the rainfall. 

This doesn't tell the whole story about which grasses perform best in a certain area. We can also consider the winter temperatures, the summer temperatures, the timing of rainfall and dry seasons, etc., but simply plotting by temperature and sunshine tells us a lot. 

Turfgrass managers in Southeast Asia know that zoysiagrass (Zoysia matrella) and broadleaf carpetgrass (Axonopus compressus) thrive in this climate while bermudagrass maintained as a turfgrass struggles. This type of plot helps us to understand why. At the Marukatayawan Palace in Thailand, we see that zoysia grows in the sun and broadleaf carpetgrass covers the shaded areas under the trees.


These native grasses thrive when maintained as turfgrass in this region, while grasses such as bermudagrass which have a higher light requirement cannot compete with zoysia even in full sun. Why is that? Because even in full sun, there is still relatively little sunshine in Southeast Asia compared with Florida.

Try This Technique for Improving Drainage


It is always a challenge to manage areas with poor drainage, and on sandcapped turfgrass areas the drainage can be quite problematic once organic matter builds up over the sand layer. Topdressing and aerififying and verticutting can all be used to dilute or remove organic matter, but when the organic layer gets too thick, it holds a lot of moisture, negating the value of the sandcap and creating an ideal growing environment for weeds.

Sand_om_layer The image above shows how an organic layer develops on a sandcapped fairway, and the image at right shows how weedy species have colonized the surface of what was once a zoysia fairyway. The buildup of organic matter over sandcapped fairways is why I have often suggested that sandcapping is not an ideal way to construct a fairway. Sandcapped fairways require more maintenance and deteriorate over time. Topdressed fairways, on the other hand, require less maintenance and improve over time.

But no matter what type of soil you have, this tip from Larry Gilhuly at the USGA is one that might be useful for you. Have you ever encountered areas with excessive organic matter buildup that slows water from infiltrating into the soil? Gilhuly asks,

"Can this condition be easily fixed at no cost or should all of these locations have complete renovation? . . . Sand topdressing and regular aeration are used to help negate the problems of excess organic material, but often this is not enough. After testing several methods to dry these areas, Rich Taylor, CGCS, struck upon the idea of using cup cutters spaced every one to two feet to go as deep as possible. The excessive organic material and some soil is removed and replaced with sand. This change essentially creates multiple dry wells in the area. If the soil underneath has reasonable permeability, the results are fast and effective. Follow-up sand topdressing is then practiced to minimize future layers. In the past few years, previous wet areas around the greens are now gone by using this simple technique."

Read the entire article on the USGA website here.

New Information on Diseases and Cation Exchange Capacity

I've been really busy in the past month, returning to Thailand after the exciting Masters Tournament, traveling to Singapore, Vietnam, and Sri Lanka, studying, and writing. Thanks to @daisukeiw who sent me the image above of the layout for my new series in Golf Course Seminar magazinePitchcare Oceania have just published a panel report on cation exchange capacity (CEC) and have featured some comments from me about CEC in sand rootzones and how it can be estimated most accurately by using an equation in which the only variables are soil pH and soil organic matter content.


I've also made some international updates to the Turf Diseases website. Some of my recent posts on that site are:

Large Patch Resistance of Zoysia?

A Cornucopia of Disease in Southeast Asia

Healthy Grass = Little Disease

Potassium, Hokkaido, and Snow Mold

Turfgrass Diseases in India

What is the Most Interesting Disease in the World?

Mites, a Corpse Plant, and Native Grasses

Large Patch on Zoysiagrass

More About Seashore Paspalum

A Most Unsightly Disease

The Wow Factor, Seashore Paspalum, and Dollar Spot