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Estimation of the Wheat Losses Caused by the Tropospheric Ozone ...

Estimation of the Wheat Losses Caused by the Tropospheric Ozone ...

Estimation of the Wheat Losses due to Tropospheric Ozone 637the past ten years. Newly designed open top chambers (OTC) allow systematicstudy, leading to quantifiable estimates for use in policy analysis. To report onearly progress, a number of meetings were carried out during the 1990’s, e.g. inSwitzerland in 1993 ([4]), and in Finland in 1995 ([6]). Among the recommendationsfrom these meetings, a new parameter called AOT40 was introduced ([4]and [6]). This parameter was suggested to be applied to agricultural and economicassessments and subsequent modeling of benefits associated with reducedozone exposure. The AOT40 parameter is commonly accepted now, also in thediscussions of the forthcoming EU Ozone Directive (see [1,3]).The value 40 ppb is a practically determined threshold, below which the lossesof crops due to ozone exposure could be neglected, and above which the lossesare assumed to be linear with respect to the exposure. The choice of AOT40is based on a large number of OTC experiments in Europe and in the UnitedStates.In this work wheat losses in Bulgaria and Denmark for a period of ten yearsare calculated by using AOT40 values produced by the Danish Eulerian Model(DEM) [10,11]. Our work on these problems started a year ago [2]. Since thenthe model was improved significantly in its chemical part and in the vertical exchangethrough the boundary layers in accordance with the knowledge obtainedby analyzing new measurement data. In addition a new release of emissionsdata from the EMEP inventories is used as an input in DEM now. All thesedevelopments lead to certain differences in the results, presented in this paper,in comparison with [2]. We believe our new estimates are much more accurate,although many uncertainties still remain.2Data Sets Used in the StudyThe following data files are used in the calculations:– The AOT40 values on the EMEP grid for each year in the period 1989 – 1998(only the values on the parts of the grid covering Bulgaria and Denmarkare used). These are produced by DEM and verified by comparisons withmeasurements and with results, obtained by other models. The maps withthe AOT40 values over Bulgaria for 1990 and 1994 are shown in Fig. 1;– The relationship between the AOT40 and the wheat loss, based on experimentsin OTC, presented at meetings in Switzerland and Finland [5,4,7];– The wheat yield in Bulgaria and Denmark by regions for the years underconsideration, taken from the corresponding Statistical Yearbooks [8,9].3 Calculating the Losses by RegionsThe basic assumption behind introduction of the excess ozone concept andAOT40 in particular is that the relative yield of wheat linerly depends on thevalue of AOT40. Provided that y is the actual yield, y + z is the expected yield

638 Tzvetan Ostromsky et al.310 326 428 441 441 447 447 458 503 513 543 555 562330 333 457 477 489 496 500 503 504 513 538 551 561330 337 459 477 492 503 503 507 508 515 524 531 546333 341 459 476 497 512 519 520 520 520 523 527 527348 353 459 476 496 512 519 523 524 523 523 522 516406 421 458 471 496 511 515 524 527 526 524 523 516440 440 451 468 493 509 512 527 532 531 526 526 517445 448 448 461 486 499 506 525 537 538 533 532 524440 439 443 451 479 490 506 520 540 542 550 553 550433 433 434 445 470 485 500 511 554 574 595 601 582410 404 404 411 444 468 500 507 557 589 618 618 618403 403 403 403 439 450 497 502 557 583 621 650 650347 341 341 348 397 407 464 489 547 547 595 610 674177 186 237 259 269 280 300 319 413 435 481 514 519191 192 302 323 324 337 337 345 417 436 477 508 515194 198 304 329 333 339 342 361 420 440 477 501 514237 255 369 394 396 396 396 399 420 441 467 488 496239 263 382 395 397 397 397 406 420 427 430 454 468300 314 382 395 397 397 397 408 414 427 430 446 455324 336 382 392 395 395 395 400 402 422 428 442 442368 369 373 384 386 386 386 390 401 417 422 440 442367 367 367 367 367 367 367 372 407 417 430 453 454364 364 364 364 364 363 362 363 407 432 466 486 488353 347 338 335 332 332 332 341 415 443 482 518 531345 344 335 333 331 331 331 337 436 445 488 532 563279 284 297 309 315 325 329 337 445 454 502 534 562Fig. 1. AOT40 maps of Bulgarian region for 1990 and 1994without any ozone exposure, ξ is the AOT40 in ppb-hours, this linear regressioncanbeexpressedasfollows:100 y/(y + z) =αξ + β (α

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